Cream together the butter and both sugars until combined.
Add the egg and vanilla extract, and mix until smooth.
Add the flour, oats, baking powder, and salt all at once, and mix into a dough.
Fold the chocolate chips into the dough. The dough will be slightly sticky, that’s perfectly fine. If it feels too sticky, you can chill it briefly in the refrigerator, but this isn’t necessary for this recipe.
Scoop the dough into balls and place them on a baking sheet lined with parchment paper. Slightly flatten the dough balls if needed.
Bake for 12-15 minutes at 375°F/180˚C (conventional oven), or until the edges turn golden brown.
How to store
Store the cookies in an airtight container and they’ll keep well for up to a week.