In a medium bowl, whisk the brown sugar (100 grams/ ½ cup), granulated sugar (100 grams/ ½ cup), flour (75 grams/ ½ cup + 2 tablespoons), cinnamon (1 ½ teaspoons), and salt (one pinch) together.
Stir in the melted butter (56 grams/ 4 tablespoons) and mix with your hands until crumbly.
Use to top muffins, coffee cakes, batter breads, or in place of a top crust on a pie. This streusel topping can be made in advance and kept in an airtight container in the refrigerator for 3 days prior to using as a topping.
