1.  Preheat oven to 350F and grease a 9 by 9-inch square pan (you can also line the pan with aluminum foil and grease the foil). Doubling the batch? Use a 9 by 13-inch pan.
2.  Melt the butter and chocolates in a medium to large saucepan over low heat, or use a microwave.  Watch carefully.
3. Meanwhile, gently beat the eggs in a bowl and stir in the vanilla.
4. When the butter and chocolate mixture is melted, take it off the heat and stir in the sugar, then the eggs and vanilla.  Add the flour (and cocoa powder, if using) and stir well with a spoon or whisk, but do not overmix.
5. Pour the brownie batter into the prepared pan. (If you're using chocolate chips or nuts, mix them into the batter first and/or sprinkle them on top of the batter before baking, pressing them down a bit into the batter.)
6. Bake for 30 to 35 minutes, or until a knife or a toothpick inserted in the center comes out almost clean.  Let the brownies cool before lifting them out from the pan.

Makes 9 to 12 brownies.

Reprinted with permission from The Treats Truck Baking Book: Cookies, Brownies & Goodies Galore! by Kim Ima, published by William Morrow Cookbooks. Photo credit: Hartini, hartini.com