Preheat your oven to 375°F (190°C).

In a large mixing bowl, combine softened unsalted butter, large eggs, and pistachio instant pudding mix. Blend on medium speed until smooth and creamy, about 2-3 minutes.

Gradually fold in the sugar cookie mix using a spatula until a sticky dough forms.

Grease a 10 x 15-inch baking sheet with cooking spray or butter and press the dough evenly into the prepared baking sheet.

Bake for 18 to 22 minutes, keeping an eye on the edges for a lightly golden color.

Remove the sheet from the oven and let it cool completely on a wire rack for about 30-45 minutes.

Once cooled, cut the bars into squares and serve.