Preparation

• Position a rack in the center of the oven and heat the oven to 350°F. Spray two 8-inch round pans with cooking spray and flour them. (If making cupcakes, line 24 standard-sized muffin cups with paper liners.)
• 的碗站与paddl搅拌机e attachment (or in a large bowl using an electric hand mixer), beat the butter, dark brown sugar, and granulated sugar together at medium speed until fluffy and lighter in color, stopping to scrape down the sides of the bowl with a rubber spatula to make sure there are no butter lumps, about 5 minutes.
• Add the eggs one at a time until completely combined.
• Put the cocoa powder in a medium heatproof bowl. Pour in 2 cups of hot tap water and whisk to dissolve the cocoa powder. Whisk in the milk and set aside.
• In a separate medium bowl, combine the flour, baking soda, and salt.
• Slowly add about one-third of the dry ingredients to the butter mixture and mix on low speed until incorporated. Continue adding the dry and wet ingredients one-third at a time, alternating between the two and ending with the dry ingredients, stopping occasionally to scrape down the sides of the bowl with a rubber spatula.
• Divide the cake batter evenly between the prepared cake pans (or muffin tins) and bake, rotating the pans’ positions halfway through baking, until a toothpick inserted in the center of a cake comes out clean or with a few moist crumbs clinging to it, 25 to 30 minutes (15 to 18 minutes for cupcakes).
• Transfer the cakes to a rack to cool in the pan for about 30 minutes. To invert, run a knife or thin metal spatula around the edge of one cake to help loosen it. Invert the cake onto a plate. Remove the cake pan. Place a cake plate on top of the cake, and invert it again so the cake plate is on the bottom. Repeat for the other cake. Transfer cupcakes to a rack to cool in the pans for about 10 minutes before turning them out onto a plate or countertop.
• Let the cakes cool completely before frosting or storing.

Make Ahead Tips

Once cool, the unfrosted cakes can be wrapped in plastic wrap and refrigerated for up to 2 days. Cupcakes are best when frosted and served the day they’re baked.