Blueberry Swirl Muffins with Lemon-Sugar Topping

I am not a fan of dense, heavy, dry muffins. And since a lot of muffins fall into this category, I've never been a big fan. But when I found this recipe for blueberry muffins in Cook's Illustrated "All-Time Best Recipes" issue, I was hooked. The key is to make a jam and swirl it through the muffins to add blueberry flavor, as opposed to just weighing it down with lots of whole blueberries (though a few of those are important, too).

This has become one of my go-to recipes for morning meetings and gatherings. People seem to really enjoy them. And for me, blueberry and lemon is an idea flavor combination. (See one of my favorite cake recipes.)

Here's how to make them. (Please note this isn't a one-pot recipe...)

BLUEBERRY SWIRL MUFFINS

For the lemon-sugar topping:
Combine 1/3 c. sugar and 1 1/2 tsp. fresh lemon zest in a bowl and set aside.

For the muffins:
2 c. blueberries
1 1/8 c. + 1 tsp. sugar
2 1/2 c. all-purpose flour
2 1/2 tsp. baking powder
2 large eggs
1 c. buttermilk
1 tsp. salt
4 T. unsalted butter, melted and cooled
1/4 c. vegetable oil
1 1/2 tsp. vanilla extract

Adjust oven track to upper-middle position and heat oven to 425. Spray 12-cup muffin tin with vegetable oil spray, line with paper if you wish.

Bring 1 c. blueberries and 1 tsp. sugar to simmer in a small saucepan over medium heat. Cook, mashing berries with a spoon and stirring frequently, until berries and broken down and mixture is thickened and reduced to 1/4 cup (about 6 mins.). Transfer to a small bowl and let cool to room temperature while you making the batter (about 15 mins.).

Whisk flour, baking powder, and salt together in a large bowl. Whisk remaining 1 1/8 c. sugar and eggs in a medium bowl until thick and homogenous, about 45 seconds. Slowly whisk in butter and oil until combined, then buttermilk and vanilla. Using a rubber spatula, fold egg mixture and remaining 1 c. blueberries into flour mixture until just moistened (do NOT overmix; dry spots will remain).

Divide batter evenly among prepared muffins cups and mound slightly. Spoon 1 tsp. cooked blueberry jam into the center of each and swirl in a figure-8 motion using a chopstick or skewer. Sprinkle lemon sugar topping evenly over muffins.

Bake until golden brown and toothpick inserted into center comes out with a few moist crumbs attached, about 17 minutes. Rotate the pan halfway through baking. Cool for at least 5 minutes before serving.