
The most perfect blueberry muffins! These are fluffy, soft muffins. They are studded with gorgeous blueberries throughout and topped with a buttery sugar streusel!
In a small bowl, make the streusel. Combine flour, white sugar, and cold cut up butter. Using your hands, mix it together until combined into a crumbly, streusel mixture. Set aside while you make the muffin batter.
Preheat the oven to 425℉/218℃. Line your muffin tin with 12 liners and set aside. Melt the butter and prepare to measure the rest of your ingredients as it cools.
In a large bowl, whisk melted and cooled butter, white sugar, egg, egg yolk, buttermilk, oil, and vanilla. Whisk until combined.
Add in flour, salt, cornstarch, baking soda, and baking powder. Using a spatula, gently fold until just combined. It's important not to over mix with muffins.
In the bowl with the blueberries, add 1-2 tsps of flour and gently toss around until evenly coated. The light coating of flour will absorb any extra liquid it may have before adding it into the mixing bowl.
Add the blueberries and mix in a few times.
Evenly divide the batter between 12 muffin liners. You can bake them all in 1 tin, or 6 in 2 tins for a taller rise. Sprinkle streusel on top.
Bake the muffins at 425°F for 5 minutes, then turn down to 375°F and bake for an additional 12-15 minutes. The muffins are ready when a toothpick inserted comes out dry with no wet batter.
These muffins are best eaten fresh. They stay fresh covered at room temperature for a few days, or in the refrigerator in an airtight container for up to 1 week!