Step 1: Preheat the oven

• Set your oven to 350°F (175°C) and line a baking sheet with parchment paper or a silicone baking mat to ensure the cookies don’t stick.

Step 2: Mix dry ingredients

• In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set the bowl aside.

Step 3: Cream the butter and sugar

• In a large bowl, beat the softened butter and sugar together until light and fluffy. This can take about 2–3 minutes with an electric mixer or a hand whisk.

Step 4: Add egg and vanilla

• Beat in the egg and vanilla extract until fully incorporated. Make sure the mixture is smooth and creamy.

Step 5: Gradually add the dry ingredients

• Slowly add the dry ingredients to the wet mixture, mixing until combined. Be careful not to overmix; stir just until the flour is incorporated.

Step 6: Fold in the blueberries

• Gently fold the blueberries into the dough. If you’re using frozen blueberries, be careful not to crush them too much. Add in any optional ingredients like lemon zest or oats at this stage.

Step 7: Scoop dough onto the baking sheet

• Using a tablespoon or a cookie scoop, drop rounded balls of dough onto the prepared baking sheet, spacing them about 2 inches apart. You should have about 24 cookies.

Step 8: Bake the cookies

• Bake the cookies in the preheated oven for 12–15 minutes, or until they’re golden around the edges. Keep an eye on them, as baking times can vary depending on your oven.

Step 9: Cool the cookies

• Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely. This helps them firm up and hold their shape.