Lemon Curd Cupcakes with Lemon Swiss Meringue Buttercream 檸檬杯子蛋糕配檸檬瑞士蛋白奶油霜

These were another cupcakes (other than the Double Chocolate Cupcakes) that I baked last week. They were extra lemony because of the sweet and tart homemade lemon curd filling hidden inside. Adding filling to the center of cupcakes has always been a surprise. I love to peek at my friends and observe their reactions after their discovery. They were always amazed and would ask me how that was possible. The trick is actually very easy and I have provided two methods of filling the cupcakes below.
這是EC上星期焗的第二批杯子蛋糕(另一款是雙重朱古力杯子蛋糕)，蛋糕充滿檸檬的清香，內裡更有酸酸甜甜的自家製檸檬醬內餡。把內餡藏進杯子蛋糕中央永遠能帶給別人驚喜，EC很喜愛偷偷觀察朋友們發現蛋糕暗藏餡料時的反應，他們常對此嘖嘖稱奇，然後問EC怎樣做到。其實為杯子蛋糕注餡一點兒難度也沒有，EC在做法中亦提供了兩個方法。

The cupcake was based on my Easy Vanilla Cupcakes recipe. I tweaked it by substituting sour cream for the plain yogurt and incorporating freshly squeezed lemon juice as well as grated zest into the batter. The Swiss meringue buttercream was flavored slightly with lemon zest and the leftover lemon curd filling. It is quite similar to my Triple Lemon Cupcakes recipe which is the older version, only that the cupcakes are now moister and that the buttercream is a lot more painless and faster to prepare.
杯子蛋糕食譜源自簡易雲尼拿杯子蛋糕，EC用酸忌廉取代原味乳酪，另外亦在麵糊中添進新鮮檸檬汁及皮蓉。而瑞士蛋白奶油霜則以檸檬皮蓉和餘下的檸檬醬內餡調味，這與舊有檸檬杯子蛋糕配方很相似，但新配方的杯子蛋糕更濕潤，而奶油霜製法也更簡便。

Lemon Curd Cupcakes with Lemon Swiss Meringue Buttercream
檸檬杯子蛋糕配檸檬瑞士蛋白奶油霜

Makes 12
12個份量

Ingredients

For the Lemon Cupcakes
100 g cake and pastry flour
80 g all-purpose flour
90 g granulated sugar (I used organic cane sugar)
3/4 tsp baking powder
1/4 tsp baking soda
1/4 tsp salt
90 g unsalted butter, softened
25 g grapeseed oil (or any light tasting oil)
120 g sour cream
2 large eggs
2 Tbsp (about 40 g) homemade invert sugar (may be replaced with light corn syrup, maple syrup or honey)
1/2 tsp vanilla bean paste or pure vanilla extract
1 Tbsp lemon juice
1 tsp grated lemon zest

For the Lemon Curd
4 Tbsp lemon juice
1/2 tsp grated lemon zest
70 – 100 g granulated sugar (adjust to taste)
55 g unsalted butter, softened and diced
3 large egg yolks
2 tsp cornstarch
1/8 teaspoon salt

For the Lemon Swiss Meringue Buttercream
100 g egg whites (from about 3 large eggs)
70 g granulated sugar
1/8 tsp salt
250 g unsalted butter, slightly softened and cubed
1/2 tsp grated lemon zest
Lemon curd, to taste

Notes: The eggs I use are about 50 g each without shells.

材料

檸檬杯子蛋糕
低筋麵粉 100克
中筋麵粉 80克
細砂糖(EC用有機蔗糖) 90克
泡打粉 3/4茶匙
梳打粉 1/4茶匙
鹽 1/4茶匙
無鹽牛油(放軟) 90克
葡萄籽油(或任何淡味食油) 25克
酸忌廉 120克
大蛋 2隻
自製轉化糖漿(可用粟膠，楓糖漿或蜜糖代替) 2湯匙 (約40克)
雲尼拿醬或純雲尼拿香油 1/2茶匙
檸檬汁 1湯匙
檸檬皮蓉 1茶匙

檸檬醬
檸檬汁 4湯匙
檸檬皮蓉 1/2茶匙
細砂糖 70至100克 (依口味調整)
無鹽牛油 (放軟及切丁) 55克
大蛋蛋黃 3隻
粟粉 2茶匙
鹽 1/8 茶匙

檸檬瑞士蛋白奶油霜
蛋白 100克 (約三隻大蛋份量)
細砂糖 70克
鹽 1/8茶匙
無鹽牛油 (少許放軟及切丁) 250克
檸檬皮蓉 1/2茶匙
檸檬醬適量

註：EC使用的大蛋每隻淨重約50克

Directions 做法

For the Lemon Cupcakes 檸檬杯子蛋糕
Preheat oven to 325ºF/160ºC. Line cupcake pan with paper liners. Bring eggs and sour cream back to room temperature.
焗爐預熱325ºF/160ºC，杯子蛋糕模內放紙模，雞蛋及酸忌廉從雪櫃取出回溫備用。

In a mixing bowl, sift together the flours, baking powder, baking soda, lemon zest, salt, and sugar and mix well. Add softened butter and oil. With a hand mixer or a stand mixer fitted with the paddle attachment, beat with low speed until mixture becomes sandy.
麵粉、泡打粉、梳打粉、檸檬皮蓉、鹽及糖混合放在鋼盤內拌匀，加入軟化牛油及油用電動打蛋器或座枱式攪拌器(使用攪拌槳配件)低速拌成濕沙狀。

Beat in the eggs one at a time until combined, scraping down the sides as needed.
蛋逐隻加入拌勻，需要時可清理盤邊。

In a small bowl combine sour cream, syrup, lemon juice and vanilla. Add mixture in two additions and beat with low speed until fully incorporated. Beat with medium speed for 1 minute to aerate the batter and develop the cake’s structure. Batter should be thick, smooth and free of lumps. Scrape down the sides as needed.
小碗內放酸忌廉、糖漿、檸檬汁及雲尼拿醬，分兩次加入麵糊中低速拌勻，之後轉中速打一分鐘將空氣混入麵糊及加强蛋糕組織，麵糊應是幼滑濃稠並無顆粒，需要時可用膠刮清理盤邊。

Divide batter evenly among liners. Bake until the cupcakes spring back to the touch and a toothpick inserted into the center of cupcake comes out clean, about 15 minutes in my oven. Adjust oven temperature and baking time accordingly for your own oven.
將麵糊平均分配倒入紙模中，入爐焗至蛋糕表面有彈性及竹籤插入蛋糕中央取出不沾麵糊，EC家中焗爐約需15分鐘，請自行調節焗爐火力及時間。

Cool in pan for 5 minutes. Transfer cupcakes to a wire rack to cool completely.
出爐五分鐘後將杯子蛋糕取出移到鋼架上完全放涼。

For the Lemon Curd 檸檬醬
Wash the lemons thoroughly and pat dry. Zest (avoid any of the white pith as it tastes bitter) and then juice it. In a small bowl, rub sugar and lemon zest with fingertips until fragrant. The zested sugar will be fluffy and turn pale yellow. Set aside.
檸檬徹底洗擦乾淨後抹乾，刨下檸檬皮蓉後(不要刨到白色部份否則會苦)切半榨汁，把檸檬皮蓉及糖放小碗中，用指頭捽至發香，檸檬糖會變得蓬鬆及轉為淡黃色，備用。

In a small saucepan, whisk together the lemon juice, zested sugar, cornstarch, egg yolks and salt. Cook, with constant stirring, over low heat until thickened and the temperature reaches 175°F/ 80°C. Remove from heat. Strain mixture into a bowl.
將檸檬汁、檸檬糖、粟粉、蛋黃和鹽放入小鍋中攪拌均勻後開小火一邊加熱，一邊攪拌直至混合物變得稠身，溫度達175°F/ 80°C後便可以離火，過篩倒入碗中。

While mixture is still warm, gradually stir in butter pieces until mixture is smooth and shiny. Cover bowl with plastic wrap by pushing the wrap down to touch the top of the curd to prevent a skin from forming on it while cooling. Set aside to cool.
趁暖逐少加入牛油塊攪拌至順滑有光澤，用保鮮紙貼着檸檬醬表面封好(可防止檸檬醬放涼後表面結皮)，放涼備用。

For the Lemon Swiss Meringue Buttercream 檸檬瑞士蛋白奶油霜
Before preparing the meringue, wipe the mixing bowl and the whisk attachment with paper towel and vinegar or lemon juice to remove any traces of grease. Add egg whites, sugar and salt to the mixing bowl. Set bowl over a pot of simmering water and whisk constantly until the temperature of an instant-read thermometer reaches 160°F/ 71°C in order to pasteurize the eggs (or until sugar has completely dissolved if pasteurized egg whites are used). Keep stirring while heating so the egg whites won’t be cooked.
製作蛋白霜前先將打蛋器配件及鋼盤用廚房紙沾點白醋或檸檬汁抹一次去除殘餘油污，鋼盤內放進蛋白、糖和鹽，小鍋內加水煮至微滾，將鋼盤放在小鍋上，開小火隔水用蒸氣將蛋白加熱至160°F/ 71°C進行消毒(若使用盒裝消毒蛋白只需加熱至糖溶)，其間要常常攪拌以免煮熟蛋白。

With an electric mixer or a stand mixer fitted with the whisk attachment, whip mixture on high speed until it is glossy and forms firm peak. If the bowl still feels warm, continue whipping with low speed until it is cool to the touch. Set aside.
用電動打蛋器或坐枱式攪拌器(使用打蛋器配件)將蛋白高速打發成挺身和有光澤的蛋白霜，若鋼盤仍有餘熱可用低速繼續攪拌至鋼盤溫度冷却，備用。

Place butter cubes in a separate mixing bowl and beat with the paddle attachment until fluffy. Add meringue into the bowl of whipped butter in three additions, beating well after each addition. Scrape the sides and bottom of bowl with a spatula if needed. Keep beating with low speed until mixture is completely incorporated.
將軟化牛油放在另一鋼盤用電動打蛋器或坐枱式攪拌器(使用攪拌槳配件)打至鬆發，然後分三次把蛋白霜加進已打發的牛油中，每次拌勻後才添加另一次，有需要時可用膠刮清理盤底及盤邊，低速攪拌至完全混合。

Beat in lemon curd and zest until incorporated.
加入檸檬醬及皮蓉拌至混合。

To Assemble 裝組
Prepare a pastry bag with a Bismarck tip (I use Wilton’s #230 tip) then fill bag with lemon curd filling. Poke tip about halfway into the cupcake and squeeze filling into the center. Pull the tip straight up slowly as you squeeze. When you feel the cupcake expanding, stop squeezing and pull the tip out. Alternatively, use a cupcake corer or a paring knife to cut out a small piece of cake from the top of the cupcake. Fill cavity with two teaspoons of lemon curd then smooth the top. Repeat until all cupcakes are filled.
將檸檬醬倒進已放長泡芙花嘴的唧袋中(EC用Wilton #230花嘴)，將花嘴插入杯子蛋糕中央後注入餡料，一邊注入一邊慢慢將唧袋往上移，當感到杯子蛋糕膨脹後便可停止並將花嘴完全抽出，沒有花嘴可用杯子蛋糕挖孔器或小刀在杯子蛋糕頂部切一小洞，將約2茶匙檸檬醬填滿洞中再抹平表面，重複將餡料注入所有杯子蛋糕內。

Prepare another pastry bag with a large star piping tip then fill bag with buttercream. Pipe a rosette on top of each cupcake. Cupcakes may be refrigerated but should be served at room temperature.
將奶油霜倒進另一已備大號星形花嘴的唧袋中，把奶油霜逐一唧在杯子蛋糕上，杯子蛋糕可放雪櫃保存但需待回溫後才食用。