Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper.

Whisk melted butter, brown sugar, and granulated sugar until smooth.

Whisk in the egg and vanilla extract.

Add flour and baking powder. Mix just until combined.

Fold in chocolate chips/chunks.

Roll dough into equal balls and place on the baking sheet, spaced apart.

Bake for 5 minutes.

Remove the tray and gently press each cookie with a fork to slightly flatten/shape.

Return to oven and bake 5–7 minutes more, until edges are set and centers look soft.

Cool 5 minutes on the pan, then move to a rack to cool.