One Bowl Milk Chocolate Cake with Chocolate Caramel Frosting

I've posted lots of chocolate cake recipes over the years, including Milk Chocolate Cakes, but mostly they use only cocoa as the main chocolate ingredient. Since today is National Milk Chocolate Day, I thought I'd post this awesome recipe from Rhoda Boone at Epicurious,  that uses both cocoa and milk chocolate bars. I'm not much for making chocolate layer cakes, and this One Bowl Milk Chocolate Cake is awesome. The Chocolate Caramel Icing is pretty great, too! I sprinkle the icing with a bit of sea salt. Yum.

ONE BOWL MILK CHOCOLATE CAKE WITH CHOCOLATE CARAMEL FROSTING

Ingredients

Cake: 
1 cup unsalted butter, plus more for pan
1/2 cup plus 2 tablespoons unsweetened cocoa powder, divided
6 ounces high-quality milk chocolate, chopped
3 large eggs
2 tsp Madagascar vanilla extract
1 3/4 cups sugar
1 1/4 cups buttermilk
2 1/2 cups all-purpose flour
1 1/2 tsp baking powder
1/2 tsp baking soda
1/2 tsp kosher salt

Frosting:
9 ounces high-quality milk chocolate, divided
1 tsp Madagascar vanilla extract
1/4 tsp kosher salt
3/4 cup heavy cream
1/2 cup store-bought dulce de leche or caramel sauce

Directions

Cake:
Preheat oven to 350°F. Butter 13x9" pan and dust with 2 Tbsp. cocoa powder, tapping out excess.
Melt remaining 1 cup butter in small saucepan over medium heat. Add chocolate and remaining 1/2 cup cocoa powder; cook, whisking constantly, until smooth. Let cool slightly.
Whisk eggs and vanilla in large bowl. Add sugar and whisk until smooth, lightened in color, and slightly aerated, about 2 minutes. Stream in buttermilk while whisking, then stream in chocolate mixture while whisking until smooth.
Sift flour, baking powder, baking soda, and salt into chocolate mixture. Whisk until batter is mostly smooth (there will be a few small lumps). Transfer to prepared pan.
Bake cake until tester inserted into  center comes out clean, 35–40 minutes. Transfer pan to wire rack and let cake cool completely.

Frosting: 
Slice 2 ounces chocolate into long, thin shards; reserve for decorating. Coarsely chop remaining 7 oz. chocolate and transfer to a medium bowl. Add vanilla and salt.
Heat cream in  small pot over medium until just starting to simmer. Pour over chocolate mixture and let sit 3 minutes. Whisk until chocolate is melted and smooth. Whisk in dulce de leche. Chill until firm, at least 1 hour.
Whisk frosting to lighten and loosen, then use spatula to spread over cake. If it's too stiff to work with, let it sit out on the counter for a few minutes. Sprinkle with reserved chocolate shards.  (I sprinkle with sea salt, too!
Cut into thirds lengthwise, then into fifths crosswise (you should have 15 pieces).