In a large mixing bowl, combine the granulated sugar, brown sugar, cocoa powder, melted butter, and vegetable oil. Beat for 2 minutes. Add the egg and vanilla, and beat until combined.

Place the flour, baking powder, and salt in a small bowl and whisk to combine. Add the flour mixture to the butter mixture, and stir until fully incorporated.

Chill the dough for 30 minutes in the refrigerator.

Once the dough is chilled, preheat the oven to 350°F and line a cookie sheet with parchment paper (or a silicone baking mat).

Divide the chilled dough into 12 even portions, and roll each one into a ball. Place the cookie dough balls on the prepared cookie sheet, 3 inches apart.

Flatten the dough balls into ¼-inch thick discs, using the palm of your hand or the bottom of a drinking glass. Bake for 10 - 12 minutes, until the edges are set and the centers are puffy.

While the cookies are baking, place the peanut butter, powdered sugar, and butter in a clean mixing bowl. Beat until well combined. Divide this mixture into 12 equal portions, and roll each one into a ball. Chill in the refrigerator for 5 minutes.

Remove the cookies from the oven and immediately use a spoon to press a dip in the center of each cookie. (See the step-by-step photos in the post above for guidance.)

Allow the cookies to cool for 3 minutes. Then add a peanut butter ball to the center of each cookie, in the indentation.

Melt the chocolate chips in a bowl in the microwave. Stir well to ensure even melting. Then generously spoon melted chocolate over the peanut butter.

Enjoy these cookies warm, or allow them to cool completely so the chocolate can set.