Seriously, I've made my second batch in a week and they are heavenly, only involving two more steps then your average blueberry muffin recipe. With much credit and love to Cooks Illustrated.
Best Blueberry Muffins
Lemon Sugar Topping
1/3 cup sugar
1 and 1/2 teaspoons finely grated zest from one lemon
3 cups fresh blueberries, picked over
1 & 1/8 cups sugar, plus 2 teaspoons
2 & 1/2 cups flour
2 & 1/2 teaspoons baking powder
1 teaspoon table salt
2 extra large eggs
1/2 stick (4 TB) unsalted butter, melted and cooled slightly
1/4 cup vegetable oil
1 cup buttermilk
1 & 1/2 teaspoons vanilla
For the topping: stir together sugar and lemon zest in a small bowl until combined, set aside.
For the muffins: Adjust oven rack to upper-middle position and heat oven to 425 degrees. Bring 1 & 1/2 cups blueberries and 2 tsp. of sugar to simmer in a small saucepan over medium heat. Cook, mashing berries with spoon several times and stirring frequently until berries have broken down and mixture is thickened and reduced to about 1/3 cup, about 6 minutes. Cool to room temp, 10-15 min.
Whisk flour, baking powder and salt together in large bowl. Whisk remaining sugar and eggs together in a medium bowl, add butter and oil until combined. Add buttermilk and vanilla to egg mixture until combined. Using a rubber spatula, fold egg mixture and remaining 1 & 1/2 cups of blueberries into the flour mixture just until moistened. Do not overmix.
Divide the batter evenly among about 14 muffin cups. Spoon one teaspoon of blueberry jam into the center of each and swirl slightly with a toothpick. Sprinkle lemon sugar evenly over muffins.
Bake until muffin tops are golden brown and just firm, 17-19 minutes. Cool in tins for 5 minutes, the finish cooling on a rack. They freeze well and can be reheated in the oven for a freshly baked texture.