Preheat oven to 350°F. Line a cookie sheet with parchment paper or a silicone baking mat. If the 3/4 cup unsalted butter is not room temperature, soften it 10–15 seconds in the microwave on high.

In a large bowl, place 1 box Krusteaz Shortbread Cookie Mix and the softened 3/4 cup unsalted butter. Use a hand mixer, wooden spoon, or stand mixer to mix until a dough forms and ingredients are evenly combined.

Fold in 1/3 cup mini chocolate chips, 1/3 cup toffee bits, and 1/3 cup crushed pretzels until evenly distributed.

Scoop dough onto the prepared cookie sheet using about 2 tablespoons of dough per cookie, leaving space between cookies. If you prefer flatter cookies, gently flatten each dough ball with the palm of your hand.

Bake 10–14 minutes, until the bottoms are slightly golden brown.

Cool the cookies on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.

Once cooled, store the cookies in an airtight container.