Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking pan.
In a mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.
Blend in the instant pistachio pudding mix until well combined. If you want a greener color, add a few drops of green food coloring at this stage.
Beat in the eggs, one at a time, ensuring each egg is fully incorporated before adding the next.
In a separate bowl, whisk together the all-purpose flour, baking soda, and salt
Gradually add the dry ingredient mixture to the wet ingredients, mixing until a soft dough forms.
Fold in the chopped pistachios if you're using them. They add a delightful crunch and extra pistachio flavor.