Buttermilk Brownies

Preheat the oven to 350°F. Line an 8-inch square metal baking dish with foil, covering the edges. Drizzle with cooking spray.In a small saucepan, melt the butter over medium-high heat. Remove the pan from the heat and stir in the chocolate until it melts and becomes smooth. Allow to cool.In a large bowl, whisk together the sugar, eggs, vanilla, and salt until smooth and pale, about 30 seconds. Add the cooled chocolate mixture and buttermilk. Add the flour until smooth, then pour the batter into a baking dish.Bake until a toothpick inserted in the brownie comes out clean, 40 to 45 minutes. Transfer the pan to a wire rack and allow to cool completely. Remove the brownies from the pan, remove the foil, and cut into 12 pieces. Wrap the brownies in plastic wrap and store at room temperature for up to 5 days.For these six options, bake until a toothpick inserted in the brownie comes out clean, 55 to 60 minutes.Coconut-Macadamia: Replace the butter with 1/2 cup coconut oil and the buttermilk with 1/2 cup coconut milk. Combine 1/2 cup toasted macadamia nuts with the flour. Before baking, sprinkle 1/4 cup coconut flakes over the dough.Peanut butter and pretzels: Replace the buttermilk with 1/2 cup of peanut butter and mix 1/2 cup of the rice pieces with the flour. Before baking, sprinkle the dough with 1/2 cup chopped pretzels.Coffee beans: Mix 2 tablespoons of instant espresso powder with flour.Malt Toffee: Combine 1 cup butterscotch slices and 1/4 cup powdered malt milk with flour. Before baking, sprinkle 1/4 cup butterscotch slices over the batter.Oreo Cheesecake Batter: Mix 3/4 cup quarter oreos (about 6 cookies) with the flour. In a small bowl, combine 4 ounces of cream cheese at room temperature, 2 tablespoons of sugar, 1/4 teaspoon of vanilla extract, and 1/4 teaspoon of kosher salt until smooth. Transfer to a small zippered bag. Cut off 1 corner of the bag with scissors, then squeeze the cream cheese mixture into a swirling pattern on the dough in the pan.Honey-nutty: Substitute 1/2 cup of honey for brown sugar and use 1 full cup of sugar. Add 1/2 cup chopped, toasted nuts mixed with flour.