Blueberry Streusel Muffins

Mix the flour and sugar in a bowl, then add the cold butter cubes. Use your fingers or a fork to combine until the mixture becomes crumbly and resembles coarse sand. Set aside.

In a bowl, mix the melted butter (or oil), milk, eggs, lemon zest, sugar, and vanilla sugar (or vanilla extract) until well combined. Set aside 1 tablespoon of flour. Gradually fold the dry ingredients into the wet mixture, being careful not to overmix, as overmixing can make the muffins dense. Toss the blueberries in the reserved 1 tablespoon of flour to prevent them from sinking. Finally, gently fold in the blueberries.

Preheat your oven to 375°F (190°C). Line a muffin tin with paper liners or grease it lightly. Pour the batter into each cup, filling about 3/4 full. Using an ice cream scoop is a great idea for portioning! Add two scoops per muffin liner if needed. Generously sprinkle the streusel topping over each muffin. Bake for 20-25 minutes, or until a toothpick inserted in the center comes out clean.