Buttery Streusel Blueberry Muffin

Ingredients:

STREUSEL

• 1/2 cup (100g) dark or light brown sugar
• 1/2 cup (67g) pecans or walnuts, chopped
• 1 teaspoon ground cinnamon

MUFFINS

• 1/2 cup (115g) unsalted butter, softened to room temperature
• 1/2 cup (100g) granulated sugar
• 1/4 cup (50g) light or dark brown sugar
• 2 large eggs, room temperature preferred
• 1/2 cup (120g) yogurt/ sour cream
• 2 teaspoons vanilla extract
• 1 and 3/4 cups (220g) all-purpose flour
• 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)

Directions:

1. Preheat oven to 425F degrees. Spray two 12-count muffin pans with nonstick spray or line with cupcake liners (this recipe makes 14 muffins, so there will be two batches). Set aside.
2. Make the streusel: In a small bowl, toss together the brown sugar, nuts, and cinnamon. Set aside.

Make the muffins:

1.  In a medium 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. 
2. 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. 
3. 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.
4. In a large bowl, toss together the flour, baking soda, baking powder, and salt. Pour the wet ingredients into the dry ingredients and slowly mix with a whisk. 
5. Add the milk, gently whisking until combined and little lumps remain. 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.
6. 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. 
7. Top with more streusel. Bake in batches for 5 minutes at 425F degrees, then keeping the muffins in the oven, lower the oven temperature to 350F degrees 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.
8. Allow to briefly cool before serving. Muffins stay soft, fresh, and moist at room temperature for up to 5 days. Muffins freeze well for up to 2 months.

Courtesy:
http://sallysbakingaddiction.com/2014/05/10/buttery-blueberry-streusel-muffins/