Combine softened butter with brown sugar until creamy. Add egg, salt, vanilla and mix well.
Add flour and baking powder and mix well until combined.
Wrap the dough in a plastic wrap and refrigerate 15 minutes.
Spread the dough in a circle on a baking tray with baking paper.
Top the cookie dough with your favorite toppings : almonds, marshmallows, hazelnuts, Oreo, m&m's, chocolate chips :-). You can also randomly put the toppings on top of your cookie.
Bake for 15 min at 350°F (180°C). Remove the circle and bake again for 5 minutes at 350°F (180°C). Remove from oven and leave to cool down.
