Preheat & Prep: Preheat oven to 375°F (190°C). Line a baking sheet with parchment paper or a silicone mat.
Mix the Wet Ingredients: In a large bowl, whisk together melted butter, sugar, eggs, vanilla, Greek yogurt, and milk until smooth.
Combine the Dry Ingredients: In another bowl, sift together flour, baking powder, baking soda, salt, and cinnamon.
Gently Fold Everything Together: Slowly add dry ingredients to wet ingredients, stirring gently. Do not overmix!
Add Mix-ins: Fold in your choice of chocolate chips, blueberries, nuts, or lemon zest.
Scoop & Shape: Drop 2-tablespoon-sized dollops of batter onto the baking sheet, leaving 2 inches of space between each.
Bake: Bake for 10-12 minutes, or until edges turn golden brown and centers are set. A toothpick should come out clean.
Cool & Enjoy: Let cool on the baking sheet for 5 minutes, then transfer to a wire rack. Enjoy warm or store for later!