Preheat your oven to 350°F (175°C). This step is crucial for ensuring your cookies bake evenly.
In a large mixing bowl, combine the creamy peanut butter and the packed light brown sugar. Use a hand mixer or a whisk to blend them together until smooth and creamy.
Crack in the large egg and pour in the tablespoon of vanilla extract. Mix until fully incorporated.
Sift the cocoa powder and baking soda into the peanut butter mixture. This will help avoid clumps and ensure an even distribution of the dry ingredients.
Stir everything together until just combined. Be careful not to overmix; a few lumps are perfectly fine!
Using a cookie scoop, drop rounded tablespoons of dough onto the prepared cookie sheet, leaving enough space between each scoop for spreading.
Place the cookie sheet in the preheated oven and bake for 10-12 minutes. The cookies should look slightly underbaked in the center; they will continue to cook on the sheet after being removed from the oven.
Let the cookies cool on the sheet for about 5 minutes before transferring them to a wire rack to cool completely. Now, the best part—enjoy your Thick and Soft Chocolate Peanut Butter Cookies with a glass of milk or your favorite beverage!