Preheat Oven: Preheat your oven to 350°F (175°C). Grease and line a 9x13-inch baking dish with parchment paper for easy removal.

Cream Butter and Sugars: In a large mixing bowl, beat the softened butter, brown sugar, and granulated sugar together until light and fluffy.

Add Eggs and Vanilla: Mix in the eggs one at a time, followed by the vanilla extract, until well combined.

Combine Dry Ingredients: In a separate bowl, whisk together the flour, baking soda, and salt.

Combine Wet and Dry Mixtures: Gradually add the dry ingredients to the wet mixture, mixing until just combined. Do not overmix.

Fold in Candy: Stir in the Reese’s Pieces and mini chocolate chips (if using) until evenly distributed.

Spread in Pan: Spread the dough evenly into the prepared baking dish, pressing it down with a spatula.

Bake: Bake in the preheated oven for 20-25 minutes, or until the edges are lightly golden and the center is set. Be careful not to overbake, as you want the bars to stay soft.

Cool and Slice: Let the bars cool completely in the pan before lifting them out using the parchment paper. Slice into squares or rectangles.