1stick unsalted butter, melted and slightly cooled
1/2cupsemi-sweet chocolate chips
2large eggs + 1 large egg yolk, at room temperature
3/4cup+ 2 tablespoons all-purpose flour, not packed
1/2cupunsweetened cocoa powder
1/2cupfull fat sour cream
1/2cuphot coffee OR hot water
For the Nutella filling:
For the raspberry buttercream:
1 1/4cupsfrozen raspberries (I think fresh would also work just fine)
2sticks (8 ounces) unsalted butter, VERY soft
3 1/2cupsconfectioners sugar (more if needed), sifted
1tablespoonheavy cream (more if needed)
1/4cupfresh raspberries, for decorating (optional)
For the cupcakes:
Preheat the oven to 350 degrees (F). Line a 12-cup cupcake/muffin tin with cupcake liners and lightly spray the liners with non-stick spray (optional but it does help them peel right off).
Melt the oil, butter,and chocolate together in the microwave, heating in 30 second increments, and stirring between increments each time. You can also melt the oil, butter, and chocolate over very low heat on the stovetop, but I find the microwave to be much easier. Whisk mixture until completely smooth and set aside to cool.
In a medium sized bowl combine the flour, baking soda, baking powder, cocoa powder, and salt; stir together until thoroughly combined; set aside.
In a large bowl, whisk together the eggs, yolk, sugar and vanilla together; beat until smooth. Add the cooled oil/butter/chocolate mixture and whisk until smooth. Add half of the flour mixture, then half of the sour cream. Repeat the process until everything is added, and be sure to mix until JUST combined - then quickly stir in the hot coffee/water. It's important not to over mix, here! Just stir until evenly combined.
Divide the batter among the 12 liners in your prepared pan, filling each cup 3/4 of the way full (you will have enough batter leftover to bake 4 more cupcakes). Bake for 16-18 minutes, or until a toothpick inserted in the center comes out clean. Cool *completely before stuffing with Nutella and frosting. Once cooled, use a small sharp knife to carve out a small hole in the center of each cupcake; do not discard the carved out cake piece. Fill each hole with two teaspoons of Nutella, then cover again with the carved out cupcake piece. Set aside and make the raspberry frosting.
For the raspberry buttercream:
Combine the raspberries and lemon juice in a small saucepan; bring to a simmer over medium heat. Once simmering, stir the mixture occasionally, breaking up the berries with a wooden spoon, until the raspberries have become soft enough to mash effortlessly. It will look like raspberry jam. Once the mixture can coat a spoon (you should have about 1/4 cup of raspberry puree) remove from heat. Allow mixture to cool completely before using. <--- That part is SUPER important!
When ready to make buttercream:
Place the softened butter in a large bowl or in the body of a stand mixer. With a handheld mixer, or with the paddle attachment on your stand mixer, beat butter on medium-high (scraping down the sides as needed) until completely smooth; about 2 minutes. Add in the raspberry puree and beat until completely combined; about 1 minute (don't worry if the mixture looks weird at this point). Add in the confectioners sugar, one cup at a time, on low speed. Once all of the sugar has been added, add in the cream and salt, then beat on high-speed for a full 2 minutes - this thickens up the frosting and makes it nice and fluffy. Frost cooled cupcakes as desired.