1. Preheat the oven to 350°F. Grease a 15x10x1-inch or a 13x9x2-inch baking pan and set aside.

2. In a medium bowl, combine the flour, sugar, baking soda, and salt; set aside.

3. In a medium saucepan combine water, butter, and cocoa powder. Bring mixture just to boiling, stirring constantly. Remove from heat.

4. Add the cocoa mixture to the flour mixture. Beat with an electric mixer on medium speed until combined.

5. Add the eggs, buttermilk, and vanilla. Beat for 1 minute (batter will be thin).

   Test Kitchen Tip: For this homemade brownie recipe, you'll need sour milk. To make 1 cup of sour milk, place 1 tablespoon of lemon juice or vinegar in a glass measuring cup. Add enough milk to make 1 cup total liquid and stir. Let the mixture stand for 5 minutes before using. Use 1/2 cup sour milk in the brownies and 3 tablespoons sour milk in the frosting. Discard remaining sour milk. Or reconstitute dry buttermilk by following the directions on the powdered buttermilk container.

6. Pour batter into prepared baking pan.

7. Bake about 25 minutes for the 15x10x1-inch pan, about 35 minutes for the 13x9x2-inch pan, or until a wooden toothpick inserted in the center comes out clean.

8. Pour warm Chocolate-Buttermilk Frosting over the warm brownies, spreading evenly. Cool the homemade brownies completely in pan on a wire rack. Cut into bars. Makes 24 brownies.

Chocolate-Buttermilk Frosting

1. In a medium saucepan combine the butter, cocoa powder, and buttermilk.

2. Bring the mixture to boiling. Remove from heat.

3. Add the powdered sugar and vanilla. Beat with an electric mixer on medium to high speed until smooth.

4. If desired, stir in pecans.

How to Store Leftover Buttermilk Brownies

Store leftover buttermilk brownies well-wrapped or in an airtight container in the refrigerator for up to four days, or freeze for up to two months. Bring to room temperature before serving.

Buttermilk Brownies Recipe Variations

While these brownies are a classic, there's no rule that says you can't change things up. Consider these additions or substitutions to add your own unique spin to these bars:

• Extracts: Substitute the vanilla extract with almond, orange, peppermint, or any other extract as desired. You can also add espresso powder to help boost the chocolate flavor of the cake or icing.
• Mix-ins: Mix chocolate chips or chunks, pecans, chopped candy bars, cookies, coconut flakes, toffee bits, or any other additions as desired into the brownie batter before baking.
• Toppings: Swap the pecans with walnuts, sliced almonds, or peanuts, or leave the nuts out and top the cake with fresh berries, mini marshmallows, toasted coconut, chocolate chips, sprinkles, candies, or other favorite toppings after frosting. You can also drizzle with melted chocolate or caramel sauce before serving for a decadent finish.