4 tablespoons of unsalted butter, melted & cooled slightly
¼ cup of vegetable oil
1 ¼ cup of yogurt
1 ½ teaspoon of vanilla extract
TOPPING:
½ cup of sugar
1 ½ teaspoon of grated lemon zest
Preparation
For the topping: Stir the sugar and lemon zest together in a small bowl until combined; set aside.
With the rack in the middle position, preheat the oven to 425°F. Line muffin cups with paper or silicone liners.
Bring 2 cups of the blueberries and 2 teaspoons of the sugar to a simmer in a small saucepan over medium heat. Mash the berries with a spoon several times and stir frequently, until the berries have broken down and the mixture is thickened (about 6 minutes). Transfer to a small bowl and cool to room temperature, about 10-15 minutes.
In a large bowl, mix the flour, baking powder and salt together.
Whisk the sugar and eggs together in a medium bowl until thick and homogeneous. Slowly add in the butter and oil. Whisk in the yogurt and vanilla until combined.
Add the egg mixture and the remaining 1 cup blueberries into the flour mixture until just moistened. Do not overmix.
Fill muffin cups half full with batter and top with a teaspoon of the cooked berry mixture. Use a toothpick and swirl together. Divide the remaining batter between muffin cups. Divide the remaining cooked berry mixture between muffin cups. Sprinkle the lemon sugar evenly over the muffins to finish.
Bake for 17 to 20 minutes or until a toothpick inserted into the centre of a muffin comes out blue from the berries, but without any batter.
