Blueberry Muffins

Adjust oven rack to upper-middle position and preheat oven to 425 degrees. Spray standard muffin tin with nonstick cooking spray. Bring 1 cup blueberries and 1 teaspoon sugar to simmer in 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 1/4 cup, about 6 minutes. Transfer to small bowl and cool to room temperature, 10 to 15 minutes. For the lemon/sugar topping: Stir together sugar and lemon zest in small bowl until combined; set aside. I had more than half of the lemon/sugar topping leftover; hence why I recommend only making half a batch of what was originally called for. Coarse sugar would be even better in this since regular sugar seems to dissolve into the muffin when baking, but overall the added texture was a nice contrast. Whisk remaining 1 1/8 cups sugar and eggs together in medium bowl until thick and homogeneous, about 45 seconds. Whisk flour, baking powder and salt together in large bowl. Slowly whisk in butter and oil until combined. Whisk in buttermilk and vanilla until combined. Using rubber spatula, fold egg mixture and remaining 1 cup of blueberries into flour mixture until just moistened. (Batter will be very lumpy with few spots of dry flour; do not overmix.) Use an ice cream scoop or large spoon to fill half of the muffin cups. Spoon a teaspoon of cooked berry mixture into center of each mound of batter, pushing it below the surface. Using a chopstick or skewer, gently swirl the berry filling into batter using a figure-eight motion. Fill the remaining cup with batter so that it completely fills the muffin cup. Sprinkle lemon sugar evenly over muffins. Bake until muffin tops are golden and just firm, 17 to 19 minutes, rotating muffin tin from front to back halfway through baking time. Cool muffins in muffin tin for 5 minutes, then transfer to wire rack and cool 5 minutes before serving. These muffins were great and I loved the blueberry jam in it, except I made a fatal flaw. I didn't have buttermilk on hand so I used yogurt instead. The problem was that I reached for the non-fat yogurt at the market and didn't realize it till I got home. If you don't know already, non-fat yogurt has absolutely no taste and apparently in baking, using whole or low-fat dairy products will make a huge difference in flavor. I will definitely try making these again with buttermilk or with whole or low-fat yogurt next time. I hope you can get your hands on some blueberries (or even a bag of frozen ones) and whip up these muffins for yourself.