1 ½cups(339g)salted butter, (24 tablespoons) cut into 24 pieces and softened at room temperature
⅓cupcaramel sauce (see note)
Instructions
For the cupcakes, preheat oven to 350°F. Line muffin cups with paper baking cups. In a large bowl, stir together sugar, flour, cocoa, baking powder, baking soda and salt. Add eggs, milk, oil and vanilla; using a handheld electric mixer or an electric stand mixer, beat on medium speed for 2 minutes. Stir in boiling water. The batter will be on the thinner side. Fill the muffin cups 2/3 full and bake for 18-20 minutes, until a toothpick inserted in the center comes out with moist crumbs. This recipe makes about 30 cupcakes. So you may need to bake the cupcakes in installments if you only have 1 or 2 muffin tins. Let the cupcakes cool completely on a wire rack, after removing them from the muffin tin.
For the frosting, in a medium bowl, combine the sugar, flour, cornstarch and salt. Slowly whisk in the milk until the mixture is smooth. Place a fine-mesh strainer over a medium saucepan and pour the milk mixture through the strainer into the saucepan. Cook the mixture over medium heat, whisking constantly, until the mixture boils and is thick enough that it starts to become difficult to easily whisk. This could take anywhere between 5-10 minutes, depending on your stove, heat, etc. It should bubble quite a bit at the end (be careful of the splatters) and thicken considerably.
Transfer the mixture to a clean bowl and cool to room temperature – this is extremely important! If it is even slightly warm, the frosting won’t beat up properly. I refrigerated my initial mixture overnight. If you do this, make sure to pull it out in time to let it warm back up to room temperature. If you try to proceed with the rest of the recipe and the mixture is too cold, the butter won’t absorb into the frosting like it should.
Once the frosting is completely cooled to room temperature (it should have no hint of warmth at all!), beat the mixture with the vanilla on low speed until it is well combined, about 30 seconds (a stand mixer will work best for this). Add the butter, one piece at a time, and beat the frosting until all the butter has been incorporated fully, about 2 minutes. Increase the speed to medium-high and let the mixer work it’s magic. Beat the frosting for five minutes, until it is light and fluffy. Fold in the caramel sauce. Let the frosting sit at room temperature until it is a bit more stiff, about 1 hour.
For the ganache, place the chopped chocolate in a medium bowl. Heat the cream to a bare simmer in a small saucepan. Pour the hot cream over the chocolate and let the mixture sit, without stirring, for 1-2 minutes. Whisk to combine until the mixture is glossy and smooth. Whisk in the butter until the butter is melted and the mixture is smooth. Transfer the bowl to the refrigerator and let the ganache chill until it is at piping consistency. It helps to give it a good stir, every 10 minutes or so to help it cool evenly. Don't let it harden too much in the refrigerator or it will be too stiff to pipe (if that happens, just let it sit at room temperature until it is soft again).
To assemble the cupcakes, fill a piping bag with the ganache and using a large round circle tip (I used Wilton 1A), pipe a ring on the top of the cupcake around the perimeter, leaving an open circle in the center (so basically you don't want to fill the entire top of the cupcake in with ganache - just an outer ring). Pour the toffee bits into a bowl and lightly press the edges of the ganache into the toffee bits, pressing very gently to adhere the toffee to the ganache.
Fill another pastry bag fitted with a decorative tip (like Wilton 1M) with the frosting and pipe a swirl of frosting on top of each cupcake, filling the empty space inside the ganache ring. Top with an additional sprinkle of toffee, if desired. Refrigerate and let sit at room temperature about an hour before serving to let the frosting soften to cool room temperature.
Notes
Caramel Sauce: here is my favorite homemade version. Frosting:plan ahead for the frosting, since the base takes a few hours to cool completely. If you don't want to go to the work of using the magical frosting recipe which is what I've used here, you could, by all means, sub in your favorite buttercream recipe - just don't forget to fold in some caramel sauce!