Place the butter in a medium saucepan or skillet. Cook over medium heat until the butter melts and begins to foam.

Continue cooking, stirring occasionally, until brown specks begin to form at the bottom of the pan and the butter has a nutty aroma.

Transfer the butter (including the browned bits) to a large mixing bowl, and allow it to cool for about 10 minutes.

Whisk together the flour, baking powder, and salt. Set aside.

Add the sugar and brown sugar to the cooled butter. Use an electric mixer on medium speed to beat until thoroughly combined. Add the eggs, one at a time, mixing well after each addition. Mix in the vanilla.

Reduce mixer speed to low. Add the flour mixture in three portions, alternating with the milk. Mix just until combined. Stir in the hazelnuts.

Divide the batter among the prepared pans, using about 3 tablespoons of batter to fill each cup about 3/4 full.

Bake 18 to 22 minutes, or until a pick inserted into the center comes out clean.

Cool the cakes in the pans for 10 minutes. Then transfer the cakes to a wire rack to cool completely.

Place the chocolate and cream in a microwave-safe bowl. Heat in the microwave for 1 minute.

Let the mixture sit for 5 minutes. Then, stir or whisk until smooth.

Spoon the ganache over the cakes. Sprinkle with reserved chopped hazelnuts.