Preheat your oven to 350 degrees Fahrenheit.
In a large mixing bowl or in the bowl of a stand mixer, cream together the 1/2 cup softened butter, 4 tbsp margarine, 3/4 cup brown sugar, and 1/4 cup granulated sugar until light and creamy.
Add 1 egg, 1 egg yolk and 2 tsp vanilla into the cookie dough and beat again until just combined.
Add 1/2 cup peanut butter and beat again.
Finally, add 2 cups flour, 1 tsp baking soda, and 1/4 tsp salt and beat until just combined. Do not overmix.
Scoop the cookie dough onto a parchment-paper lined cookie sheet using a #40 cookie scoop (2 Tbsp worth of dough).
Bake in the preheated oven for 8-10 minutes or until the edges turn brown but the centers are still soft.
Allow the cookies to cool on the baking sheet for a few minutes. After 5 minutes, transfer the cookies to a wire rack to cool the rest of the way.
Serve and enjoy!