Preheat the oven to 350 degrees.
Mix the dry ingredients in a large bowl.
Cut the butter into the flour mixture with a pastry cutter until it looks like coarse sand.
Set aside one cup of the flour mixture in a small bowl for the streusel topping.
Add the eggs, buttermilk, and vanilla to the flour mixture and stir with a wooden spoon.
Carefully fold in the blueberries with a spatula.
Add two tablespoons of melted butter to the one cup of flour mixture that was set aside. Use a fork to cut the melted butter into the mixture for the crumb topping.
Place muffin liners in muffin tins.
Divide batter among the 24 muffin cups. Use a large spoon and a spatula to scrape the batter in each muffin tin. The approximate amount of batter for each muffin is the size of an ice cream scoop.
Place the crumb topping on each muffin. The crumb topping is not very crumbly, so you will need to use your fingers to separate it into small pieces. This topping will melt into the muffin tops and create a buttery, crunchy texture.
Cook at 350 degrees for 18 to 23 minutes or until the tops are golden brown.
Cool on a wire rack.
Serve warm with butter.
Store in an airtight container on the counter for three to four days or freeze for up to three months.