Preheat oven to 350°F. Line a 9x13-inch pan with aluminum foil and spray the bottom and sides with cooking spray, and set aside.
In a large bowl with a hand mixer or in a stand mixer fitted with a paddle attachment, cream together the ½ cup unsalted butter, ½ cup granulated sugar, ½ cup light brown sugar, 1 large egg, and 2 teaspoons vanilla extract.
In a separate bowl, combine 1½ cups all-purpose flour, ¾ teaspoon salt, and ½ teaspoon baking soda, then add the flour mixture to the wet ingredients in two separate additions, mixing until combined after each addition.
Mix in 1 cup of the 1¼ cup semi-sweet chocolate chips.
Transfer the cookie dough to the prepared baking pan and use your hands to press and spread the dough out evenly to cover the entire pan.
Sprinkle the remaining 1/4 cup of mini chocolate chips over the dough, then gently press them into the dough with the palms of your hands.
Bake for 18 to 22 minutes until edges are golden brown.
Remove from the oven, gently lift the cookie out of the pan using the aluminum foil, and transfer to a solid, flat surface.
Use a pizza cutter to cut 18 strips along the 13-inch side and then run the cutter once up the middle of the 9-inch side to create 36 cookie sticks.