1. Preheat and Prepare: Preheat your oven to 350°F (175°C). Grease and flour a 9×13 inch baking pan, or line it with parchment paper, leaving an overhang on two sides to easily lift the brownies out later. This step is crucial for preventing sticking and ensuring clean slices.

2. Melt Butter: In a large microwave-safe bowl, or in a saucepan over low heat, melt the butter for the brownies. Be careful not to let it boil, just melt it completely.

3. Combine Wet Ingredients (Brownies): To the bowl with the melted butter, add the granulated sugar. Whisk them together until well combined. It might look a bit grainy, and that’s okay. Add the eggs one at a time, beating well after each addition until the mixture is smooth and slightly lightened. Stir in the vanilla extract.

4. Combine Dry Ingredients (Brownies): In a separate medium bowl, whisk together the all-purpose flour, unsweetened cocoa powder, baking powder, and salt. This helps to distribute the ingredients evenly and remove any lumps from the cocoa powder.

5. Combine Wet and Dry: Gradually add the dry ingredient mixture to the wet ingredient mixture. Mix on low speed with an electric mixer or by hand with a wooden spoon or spatula until just combined. Be very careful not to overmix at this stage; overmixing develops gluten and can lead to tough, cakey brownies instead of fudgy ones. Stop mixing as soon as you no longer see streaks of flour.

6. Spread Batter: Pour the brownie batter into your prepared 9×13 inch baking pan. Use a spatula to spread it evenly, ensuring it reaches all corners of the pan. The batter will be thick.

7. Bake the Brownies: Bake in the preheated oven for 25-30 minutes. The baking time can vary depending on your oven. To check for doneness, insert a toothpick into the center of the brownies. It should come out with moist crumbs attached, but not wet batter. If it comes out clean, they might be overbaked. For fudgier brownies, err on the side of slightly underbaking.

8. Cool Brownies: Once baked, remove the brownies from the oven and place the pan on a wire rack to cool completely. This is a very important step! Attempting to frost or cut warm brownies can result in a messy disaster. Allow at least 1-2 hours for them to cool thoroughly. Patience here will be rewarded.

9. Prepare the Frosting: While the brownies are cooling, or once they are completely cool, prepare the chocolate frosting. In a medium bowl, using an electric mixer, beat the softened butter until creamy. This usually takes about 1-2 minutes.

10. Add Cocoa and Sugar (Frosting): Sift in the cocoa powder and half of the powdered sugar. Beat on low speed until combined. Then, add the remaining powdered sugar and continue to beat until smooth. The mixture will be quite thick.

11. Add Liquid and Vanilla (Frosting): Add 3 tablespoons of milk and the vanilla extract to the frosting mixture. Beat on medium speed until the frosting is light, fluffy, and spreadable. If the frosting is too thick, add the remaining tablespoon of milk, a little at a time, until you reach the desired consistency. Add a pinch of salt to enhance the chocolate flavor.

12. Frost the Brownies: Once the brownies are completely cool, spread the chocolate frosting evenly over the top using an offset spatula or a knife. If you prefer a thinner, glaze-like frosting that sets with a slight crackle (very traditional for lunch lady brownies!), you can gently warm the frosting for a few seconds in the microwave (5-10 seconds) to make it more pourable, then pour and spread quickly.

13. Set and Cut: Allow the frosting to set for at least 30 minutes before cutting the brownies into squares. For the cleanest cuts, use a sharp knife, wiping it clean with a damp cloth between each cut. You can also chill the frosted brownies briefly to help the frosting firm up.

14. Serve and Enjoy: Serve your delicious homemade Lunch Lady Brownies and watch them disappear! Store any leftovers in an airtight container at room temperature for up to 3 days, or in the refrigerator for up to 5 days.