Preheat oven to 350°F (177°C). Line baking sheets with a silicone baking mat or parchment paper and set aside.

In a large bowl, using a stand mixer or hand mixer, beat 1 1/2 cups creamy peanut butter, 1 cup softened butter, 1 cup packed brown sugar, and 1 cup granulated sugar until creamy and well combined, scraping down the bowl as needed.

Add 2 eggs and 1 teaspoon vanilla extract to the bowl and beat until the mixture is smooth and evenly combined.

In a separate bowl, whisk together 2 cups all-purpose flour, 1 1/2 teaspoons baking soda, and 1/2 teaspoon salt.

Add the dry ingredients to the wet ingredients and mix on low speed (or stir by hand) until just combined. Do not overmix.

Fold in 1–2 cups Reese’s Pieces and any desired mix-ins: 1/2–1 cup chocolate chips (optional), 1/2–1 cup peanut butter chips (optional), and/or 1/2 cup peanuts (optional). Fold only until evenly distributed.

Using a cookie scoop or tablespoon, portion dough into mounds of approximately 2 tablespoons each and place them on the prepared baking sheets about 2 inches apart.

Bake one sheet at a time (or as many as will fit without crowding) in the preheated oven for 12–14 minutes, until the edges are set and the tops are lightly golden.

Remove the baking sheet from the oven and transfer it to a wire cooling rack. Let the cookies cool on the baking sheet for at least 5 minutes.

After 5 minutes, transfer the cookies to the wire rack to cool completely.

Yield: approximately three dozen cookies. If you have more dough than fits on one sheet, bake in additional batches, allowing the oven to return to temperature between batches if needed.