Using a cookie scoop (or an ice cream scoop, or even just a spoon), transfer ~1 tbsp of the cookie batter onto the lined baking sheet, keeping at least 1 inch between them.
Spread each scoop out slightly with a spoon, and place ~1/2 tbsp of peanut butter in the centre.
Cover the peanut butter with another ~1 tbsp of the cookie batter, spreading the batter a bit so that the peanut butter is fully covered.
The cookies are best still warm, so that the peanut butter in the centre is still runny – but they are also super delicious when cold.
These peanut butter stuffed brownie cookies keep well in a closed container in a cool dry place for about 1 week.