Preheat your oven to 375°F (190°C). Gather your mixing bowl and ingredients.

In a large mixing bowl, combine 1 cup of softened unsalted butter, 2 large eggs, and one package of pistachio instant pudding mix. Cream together until smooth and fluffy, about 2-3 minutes.

Gradually add the sugar cookie mix to your wet ingredients, mixing on low speed until a sticky dough forms, around 1-2 minutes.

Grease a 10 x 15-inch baking sheet with cooking spray or butter. Transfer the dough to the sheet and press it down evenly.

Place the baking sheet in the preheated oven and bake for 18-22 minutes until edges are light golden brown.

Remove the pan from the oven and allow it to cool completely on a wire rack for about 30 minutes.

Use a sharp knife to cut the cooled bars into squares. Drizzle melted chocolate on top if desired.