1. Preheat the oven to 400°Line a standard muffin tin with paper liners.

Brown the butter:

1. In a small stainless skillet set over medium heat, melt the butter. Swirling the pan occasionally, continue to cook the butter. It should become foamy with audible cracking and popping noises.
2. Once the crackling stops continue to swirl the pan until the butter develops a nutty aroma and brown bits start to form at the bottom. Once the bits are amber in color, about 2 to 3 minutes after the popping stops, remove from heat and pour into a medium mixing bowl. Let cool.

Make the batter:

1. In a large bowl whisk together the flour, sugars, salt, and baking powder.
2. In a small bowl whisk together the buttermilk, cooled browned butter, egg, and vanilla. Pour into the dry ingredients and stir with a rubber spatula until just combined. Gently stir in the blueberries. Do not overmix. Divide evenly among the muffin tin cups.

Make the crumb topping:

1. In a small bowl, combine all of the topping ingredients with a fork until the texture resembles wet sand.
2. Use your fingertips to sprinkle over muffin batter in pans. Bake until golden brown and a toothpick inserted in the center comes out clean, about 20 to 22 minutes. Let cool until barely warm.
3. Serve or store in an airtight at room temperature for 3 days. Reheat in the microwave for about 15 seconds if desired. Muffins can also be frozen in an airtight container for up to 3 months.