• Preheat the oven to 400ºF (204ºC).
• Spray 9 wells of a 12 count muffin pan with non-stick spray³ or line with cupcake liners. Set aside.

CINNAMON STREUSEL

• Place flour, brown sugar, cinnamon, and salt into a small bowl, then use a fork to combine.
  ¼ cup (60g) all-purpose flour, 2 Tablespoons (25g) firmly packed light or dark brown sugar, ¾ teaspoon ground cinnamon, ⅛ teaspoon salt
• Add the cubed butter, then use the fork to press ingredients together until butter is in small chunks. Use your fingers to pinch pieces together until streusel is mostly small crumbles. Some large crumbles are ok. Set aside.
  2 Tablespoons (28g) cold unsalted butter

MUFFINS

• In a medium size bowl, toss together the flour, cinnamon, baking powder, baking soda, and salt. Set aside.
  1 and ¼ cup (180g) all-purpose flour, ½ teaspoon ground cinnamon, 1 teaspoon baking powder, ¼ teaspoon baking soda, ¼ teaspoon salt
• In a large bowl with a handheld mixer or the bowl of a stand mixer fitted with the paddle attachment, cream the butter and sugars until light and fluffy. Add the eggs one at a time, beating on medium speed after each until combined. Add the vanilla and the yogurt and beat again on medium speed until completely incorporated.
  6 tablespoons (85g) unsalted butter, ½ cup (100g) firmly packed light or dark brown sugar, ¼ cup (50g) granulated sugar, 2 large eggs, 1 teaspoon vanilla extract, ½ cup (120g) full fat yogurt or sour cream2
• Pour the wet ingredients into the dry ingredients and stir gently with a spatula until no flour pockets remain. Allow the muffin batter to rest for 15-20 minutes (you do not need to cover it).
• After the batter has rested, spoon the batter evenly into the 9 wells. One ice cream scoop full works best, totaling about ¼ cup of batter in each well. Sprinkle a heaping Tablespoon of the streusel topping on each pile of batter. Bake the muffins for 5 minutes, then without opening the oven door, reduce the temperature to 350ºF (177ºC) and bake for another 13-14 minutes, or until a toothpick inserted in the center comes out clean.
• Remove from oven and allow muffins to cool in the pan at least 10 minutes before transferring to a wire rack to cool completely. Leftovers can be kept covered tightly at room temperature up to 5 days or in the refrigerator up to one week. Muffins freeze well, up to 2 months. Thaw in fridge overnight or heat up in microwave for 15 seconds on high.