Preheat your oven to 375°F (190°C).

In a large mixing bowl, combine 1 cup of softened unsalted butter, 2 large eggs, and 3.4 ounces of pistachio instant pudding mix. Cream together until smooth and fluffy, about 2-3 minutes.

Gradually add in 17.5 ounces of sugar cookie mix, stirring with a spatula until a soft, sticky dough forms.

Grease a 10 x 15-inch baking sheet with cooking spray or butter. Spread the dough evenly across the pan and press firmly into the corners.

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

Allow the bars to cool in the pan on a wire rack for about 30 minutes.

Slice the bars into squares or rectangles using a sharp knife, and serve as is or with melted chocolate drizzle.