Making Texas Sheet Cake Cookies is easy if you follow these steps:

1. Preheat Oven: Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.
2. Mix Dry Ingredients: In a large bowl, combine the flour, granulated sugar, brown sugar, cocoa powder, baking soda, and salt. Whisk until well blended.
3. Combine Wet Ingredients: In another bowl, mix the melted butter, buttermilk, eggs, and vanilla extract until smooth.
4. Combine Mixtures: Gradually pour the wet ingredients into the dry ingredients, mixing until just combined. Be careful not to overmix.
5. Add Chocolate Chips: If using, fold in the chocolate chips for added richness.
6. Scoop Dough: Use a cookie scoop or tablespoon to drop rounded balls of dough onto the prepared baking sheets, spacing them about 2 inches apart.
7. Bake: Place the baking sheets in the preheated oven and bake for 10-12 minutes, or until the edges are set but the centers are slightly soft.
8. Cool: Remove from the oven and let the cookies cool on the baking sheets for about 10 minutes. Then, transfer them to wire racks to cool completely.
9. Prepare Frosting: While the cookies cool, whisk together the powdered sugar, cocoa powder, milk, and vanilla extract until smooth.
10. Frost Cookies: Once the cookies are completely cool, spread a generous layer of frosting on each cookie. Optionally, sprinkle with chopped nuts for added texture.

These simple steps will guide you in creating delicious Texas Sheet Cake Cookies that are sure to be a hit!