Melt the butter in the microwave or in a small saucepan over low-medium heat. You don’t want it to bubble, so as to not lose any of the liquid in the butter. Pour the melted butter into a big mixing bowl and let it cool down to room temperature in the fridge. Takes about 20 minutes.
110 g butter
Once the butter has reached room temperature add the granulated sugar and brown sugar and with spatula whisk it together for 1 minute. Alternatively, mix it together in a stand mixer using the paddle attachment.
100 g granulated sugar, 100 g dark brown sugar
Add the egg, vanilla extract and mix it in until combined.
1 egg, 1 teaspoon vanilla extract
In a separate bowl, stir together flour, baking powder, baking soda, instant espresso powder and salt. Add the dry ingredients to the wet mixture and with spatula mix it together until just combined.
230 g all-purpose flour, ½ teaspoon baking powder, ½ teaspoon baking soda, 1 tablespoon instant espresso powder, ½ teaspoon salt
Using a 2 tbsp/ 1.3 ounce cookie scoop, scoop out 11 cookies and place them on a tray lined with baking paper. Then roll them between your hands into a ball. Place the prepared cookies in the fridge to set for 1 hour.
Meanwhile, preheat the oven at 180ºC / 355ºF and prepare a baking sheet with baking paper. Place 6 cookies per baking tray and bake one tray at a time for 10-11 minutes.
Once baked, let them cool down on the baking tray for 3 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 and let them cool down completely.