Step-by-Step Instructions

• Preheat your oven to 350 degrees Fahrenheit. In a large mixing bowl, cream the softened butter, peanut butter, brown sugar, and granulated sugar together until the mixture looks light and creamy. This usually takes about 2 to 3 minutes with a hand mixer or stand mixer. Scrape down the sides of the bowl once or twice so everything combines evenly.
• Add the salt, vanilla extract, and egg to the creamed mixture. Mix well until the egg is fully incorporated. Then add the baking soda and all purpose flour. Mix on low speed just until the flour disappears. Overmixing can make the cookies tough, so stop as soon as you no longer see dry streaks.
• Roll the cookie dough into 48 equal-sized balls, about 1 and 1/4 inches each. A small cookie scoop works perfectly here. Pour your rainbow sprinkles into a shallow bowl. Roll each dough ball in the sprinkles until it is completely coated on all sides. Use gentle pressure so the sprinkles stick, but try not to flatten the balls.
• Place the sprinkle-coated dough balls on ungreased cookie sheets, spacing them about 2 inches apart. Bake for 8 to 10 minutes. The cookies will look slightly puffed and set around the edges but still soft in the center. Do not overbake them.
• As soon as the cookies come out of the oven, immediately press a milk chocolate star into the center of each one. If you wait too long, the cookie will set and the chocolate will not stick. Allow the cookies to cool on the baking sheet for about 5 minutes before moving them to a wire rack. A practical tip for even baking is to rotate your cookie sheet halfway through the baking time. If you bake two sheets at once, switch their oven positions when you rotate. Keep in mind that the chocolate stars will melt slightly from the warm cookie, which is exactly what you want. Let them cool completely so the chocolate sets again before stacking or storing.