Preheat oven to 325 degrees F. Line cookie sheets with silicone baking mats or parchment paper.
In a medium bowl, whisk together flour, baking soda, and salt; set aside. With an electric mixer or by hand, beat the butter and sugars until well-combined. Beat in the egg, yolk, and vanilla extract.
Add dry ingredients and mix at low speed just until dough is evenly combined. Gently stir in the chocolate chips and about half of the sprinkles.
Portion out a large scoop of dough. (You can either use a large, 3 tablespoon dough scoop to make heaping mounds, or scantly fill a 1/4 cup measuring cup.) Roll into a ball. Hold the ball in the fingertips of both hands, and twist to pull it apart into two roughly equal halves. Place the halves onto the cookie sheet, jagged surface facing up, leaving about 2 inches between the cookies.
Bake, rotating pans halfway through, for 12-14 minutes, just until the cookies are light golden brown with slightly hardened edges and soft, puffy centers. You want to remove them just before they look completely done, so the inside stays very tender.
Immediately after removing cookies from the oven, press candy eyes into each one. You can give each cookie two eyes, some three, others one, etc. -- get creative and have fun. Add the remaining sprinkles to the tops of the cookies, as well, pressing very gently if needed to adhere.
Cool cookies on baking sheets for 10-15 minutes, then transfer to a wire rack. Enjoy!