Center a rack in the oven and preheat the oven to 325 degrees F.
Line a 9-inch square baking pan with foil, butter the foil and place the pan on a baking sheet.
To make the brownies: Set a heatproof bowl over a saucepan of simmering water and add, in the following order, the butter, the two chocolates and the coffee.
Keeping the pan over low heat, warm just until the butter and chocolates are melted-you don't want the ingredients to get so hot they separate, so keep an eye on the bowl.
Stir gently, and when the mixture is smooth, set it aside for 5 minutes. Using a whisk or rubber spatula, beat the sugar into the chocolate mixture. Don't beat too vigorously-you don't want to add air to the batter-and don't be concerned about any graininess.
Next stir in the eggs one at a time, followed by the vanilla. You should have a smooth glossy batter.
If you're not already using a rubber spatula, switch to one now and gently stir in the dry ingredients, mixing only until they are incorporated. Finally stir in the milk chocolate chips and the nuts. Scrape the batter into the pan.
Pour the ingredients into your prepared pan, and place in the oven.
Bake for about 35 minutes, or until a thin knife inserted into the center comes out streaked but not thickly coated. Transfer the pan to a cooling rack and let the brownies rest undisturbed for at least 30 minutes. (You can wait longer, if you'd like.) If you're going to add the glaze to the top, keep reading below. Otherwise, your brownies are done and they are amazing!