1/2 cup (100g) packed dark or light brown sugar
1/2 cup (67g) pecans or walnuts, chopped
1 teaspoon ground cinnamon
1/2 cup (115g) unsalted butter, softened to room temperature
1/2 cup (100g) granulated sugar
1/4 cup (50g) packed light or dark brown sugar
2 large eggs, room temperature preferred
1/2 cup (120g) yogurt1
2 teaspoons vanilla extract
1 and 3/4 cups (220g) all-purpose flour (measured correctly)
1 teaspoon baking soda
1 teaspoon baking powder
1/2 teaspoon salt
1/4 cup (60ml) milk (any kind)
1 and 1/2 cups (250g) fresh or frozen blueberries (do not thaw if using frozen)
Preheat oven to 425°F (218°C). Spray two 12-count muffin pans with nonstick spray or line with cupcake liners (this recipe makes around 14 muffins, so there will be two batches). Set aside.
Make the streusel: In a small bowl, toss together the brown sugar, nuts, and cinnamon. Set aside.
Make the muffins: In a large bowl using a handheld or stand mixer fitted with a paddle attachment, beat the butter on high speed until smooth and creamy, about 1 minute. Add the granulated and brown sugars and beat on high until creamed, about 2 full minutes. Scrape down the sides and bottom of the bowl as needed. Add the eggs, yogurt, and vanilla extract. Beat on medium speed for 1 minute, then turn up to high speed until the mixture is combined and uniform in texture. Scrape down the sides and bottom of the bowl as needed.
In a large bowl, toss the flour, baking soda, baking powder, and salt together. Pour the dry ingredients into the wet ingredients and beat on low speed until just about combined. Add the milk and continue to beat on low until combined. Fold in the blueberries with a wooden spoon or rubber spatula. Don't worry if the blueberries bleed a little - my batter was purple in some spots; it looks pretty when baked!
Layer in 1 Tablespoon of batter, then top with a little streusel, then more batter until the muffin tins or liners are full all the way up to the top. You want them overflowing, as shown in the photo above. Top with more streusel. Bake in batches for 5 minutes at 425°F (218°C) then keeping the muffins in the oven, lower the oven temperature to 350°F (177°C) and bake for 18-21 more minutes or until a toothpick inserted in the center comes out clean. The total times these muffins take in the oven is about 23-26 minutes. Allow to briefly cool before serving.