Preheat oven to 425°F Spray muffin tin pan with nonstick cooking spray. Set aside.
In a small saucepan add 1 cup of blueberries and 1 tablespoon granulated sugar. Simmer. As you’re stirring, use the back of a wooden spoon to mash some of the berries. *Simmer for 5 minutes or until thickened. Remove from heat and cool to room temperature.
In a medium size bowl whisk the flour, baking powder, and salt. Add the remaining 1 cup of blueberries to the flour mixture, toss to coat. Set aside.
In another medium size bowl whisk the remaining 1 cup of sugar and the eggs for 1 minute. Add the butter and oil whisking to combine. Finally, whisk in the buttermilk and vanilla.
Add the wet ingredients to the flour and blueberry mixture. Use a spatula to mix everything together. Don’t overmix.
Scoop the muffin batter into the muffin tins. Fill each muffin tin 3/4 full, or pretty close to the top of the muffin tin.
Spoon 1 teaspoon of the cooked blueberry mixture into each muffin tin. Use the prongs of a fork or a chopstick to swirl the blueberry mixture into each muffin tin. Sprinkle each muffin with 1 teaspoon of sugar in the raw.
Bake for 16-20 minutes. (Mine baked for 17 minutes).
Remove from oven and let the muffins cool for 3-5 minutes and then remove the muffins from the tin and let them cool completely on a wire rack.