For the blueberry swirl:
- 1 cup fresh blueberries (about 1 pint)
- 1 teaspoon sugar
- 2 1/2 cups all-purpose flour
- 1 1/8 cups sugar
- 2 1/2 teaspoon baking powder
- 1 teaspoon salt
- 2 large eggs
- 4 Tablespoons unsalted butter, melted & cooled slightly
- 1/4 cup vegetable oil
- 1 cup milk
- 1 1/2 teaspoon vanilla
- For the streusel topping:
- 1/2 cup all-purpose flour
- 1/3 cup granulated sugar
- 1/2 stick salted butter-melted
- 1/2 teaspoon cinnamon
Preheat oven to 425 degrees. Spray a standard muffin tin with vegetable oil spray (or line with paper liners and spray).
For the blueberry swirl:
- If you want to use whole blueberries in your muffin batter instead of a blueberry swirl, omit this step, toss whole blueberries with 1 additional Tablespoon of flour, and fold blueberries in after preparing batter.
- Bring blueberries and 1 teaspoon of the sugar to a simmer in a small saucepan over medium heat. Cook, mashing the berries with a spoon several times and stirring 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, 10-15 minutes.
For the muffins:
- Whisk the flour, baking powder and salt together in a large bowl. Set aside.
- In a medium bowl, whisk together 1-1/8 cups sugar and eggs until thick and well combined, about 45 seconds. Slowly whisk in the butter and oil until combined. Nest, whisk in the milk and vanilla until combined.
- Using a rubber spatula, fold the egg mixture into the flour mixture until just moistened. The batter will be very lumpy with a few spots of dry flour; do not overmix. (If using whole blueberries, fold in now.)
- Fill muffin cups 1/2 full with batter and top with a teaspoon or so of the cooked berry mixture. Use a toothpick to swirl. Divide the remaining batter between muffin cups. The batter should completely fill the cups and mound slightly. Divide the remaining cooked berry mixture between muffin cups. Use a toothpick to swirl.
Make the streusel topping:
- To make the crumb topping in a small bowl, whisk together flour, sugar and cinnamon, add melted butter and stir with a fork until crumbly. Spoon streusel over muffins.
- Bake until the muffin tops are golden and just firm, 17-18 minutes, rotating the muffin tin halfway through. Cool the muffins in the muffin tin for 5 minutes, then remove to a wire rack and cool 5 more minutes before serving. Yield: 12 muffins.