In a light colored saucepan over medium heat, melt the butter, stirring frequently. Continue cooking, swirling the pan often, until the butter turns golden brown and smells nutty — about 5–7 minutes. Watch carefully; it can burn quickly. Pour into the bowl of a stand mixer and allow to cool for 10 minutes.

Cream butter, peanut butter, and sugars. Add the peanut butter, granulated sugar, and brown sugar to the browned butter. Beat on medium speed until fully combined and smooth, about 2–3 minutes. Scrape down the sides of the bowl as needed.

Add eggs and vanilla. Add the eggs and vanilla extract. Scrape down sides of bowl and beat on medium speed until fully incorporated and slightly fluffy, about 2 minutes.

In a separate bowl, whisk together the flour, cornstarch, baking soda, baking powder, and salt. Add the dry ingredients to the wet ingredients and mix on low until just combined — do not overmix.

Using a spatula or wooden spoon, fold in the mini peanut butter cups, peanut butter chips, dark chocolate, and mini chocolate chips until evenly distributed throughout the dough.

Preheat your oven to 375°F and line a baking sheet with parchment paper. Cover the bowl and refrigerate the dough for 30 minutes.

Scoop 3 tablespoons of dough per cookie. For bakery style uniform cookies, roll each into a smooth ball and gently flatten into a thick disc, smoothing the sides. Place 2 inches apart on the prepared baking sheet.

Bake for 12–14 minutes, until the edges are lightly golden and the centers look just slightly underdone. They will set as they cool.

Finish with sea salt. Immediately upon removing from the oven, sprinkle generously with flaky sea salt. Allow cookies to cool on the baking sheet for at least 10 minutes before transferring.