Preheat the oven at 175ºC / 350ºF and prepare a baking sheet with baking paper.
In a bowl, stir together flour, baking powder, baking soda, and salt.
280 g all-purpose flour, ½ teaspoon baking powder, ½ teaspoon baking soda, ½ teaspoon salt
Add the brown sugar and granulated sugar into a separate bowl with the butter. Using an electric hand whisk, whisk it together for 2 minutes, so it becomes light and fluffy.
160 g butter, 100 g granulated sugar, 100 g brown sugar
Add the egg and vanilla extract and mix it in.
1 teaspoon tsp vanilla extract, 1 large egg
Add the flour mixture and with a spatula, fold it together until just combined. Then add the chocolate chips and fold them in.
Lastly add the chocolate chips and fold them in.
120 g chocolate chips
Using a 2 tbsp/ 1.3 ounce cookie scoop, scoop out 6 cookies at a time per baking tray. Give each cookie a gentle press down to flatten the top.
Bake one baking tray at a time for 10 minutes. Then add 8 mini marshmallows on each cookie and gently press them down on the cookie so they don’t fall off. Place the baking tray back in the oven and bake them for further 2 minutes.
A bag of mini marshmallows
Once baked, let them cool down on the baking tray for 5 minutes as they still will be soft when they are done. After they have cooled down a bit, use a spatula to lift them onto a cooling rack.