Melt the butter in the microwave or in a small saucepan over low-medium heat. You don’t want it to bubble, as to not lose any of the liquid in the butter. Pour it 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.
150 g granulated sugar, 50 g 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, cinnamon and salt. Add the dry ingredients and with spatula mix it together until just combined.
240 g all-purpose flour, ½ teaspoon baking powder, ½ teaspoon baking soda, ½ teaspoon salt, ½ teaspoon cinnamon
Using a 2 tbsp/ 1.3 ounce cookie scoop, scoop out 11 cookies and place them on a tray lined with baking paper. Using a tablespoon measurement, press the tablespoon into the middle of the cookie dough balls and press it down to make an indent in the cookie dough. Fill the indent with a tablespoon of streusel. Place the prepared cookies in the fridge to chill for 1 hour.
Meanwhile, preheat the oven at 180ºC / 355ºF and prepare a baking sheet with parchment paper.
Once the hour has passed, 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.