To a large bowl, add the cookie mix, butter, egg, and stir to combine.
Using a two tablespoon cookie scoop, or your hands, form approximately 16 equal-sized mounds of dough.
Sprinkle on or dredge each mound of dough through sprinkles.
Preheat oven to 350F, line a baking sheet with a Silpat or spray with cooking spray. Place dough mounds on baking sheet, spaced at least 2 inches apart (do not bake more than 8 cookies per sheet because these cookies spread) and bake for about 10 to 11 minutes (if your cookies are smaller, bake less; and keep a watchful eye on them since ovens very dramatically), or until edges have set and tops are just set, even if slightly undercooked, pale, and glossy in the center; don’t overbake. Cookies firm up as they cool.
Immediately after removing cookies from oven, add 1 Hershey’s Kiss to the center of each cookie, pressing it down lightly. Allow cookies to cool on baking sheet for about 15 minutes before removing. I let them cool on the baking sheet and don’t use a rack. Cookies will keep airtight at cool room temperature for up to 1 week or in the freezer for up to 6 months.