In a medium bowl, combine the Greek yogurt, protein powder, peanut butter, and sweetener. Stir vigorously with a spatula or whisk until completely smooth and well-combined, making sure there are no streaks of protein powder remaining. The mixture should have a thick, creamy consistency at this stage. I find that using a slightly thicker yogurt like Fage 5% gives you that authentic cookie-dough texture right from the start, so you may not need to add much liquid at all.

Taste the mixture and adjust sweetness if needed. If the consistency feels too thick for your preference, add a small splash of milk (start with 1 teaspoon) and stir until you reach your desired texture—it should be creamy and spoonable but still thick enough to feel indulgent. Fold in the vanilla extract and chocolate chips, distributing them evenly throughout. I like to crush some of the chocolate chips slightly before folding them in so you get pockets of chocolate throughout each bite.