Preheat the oven to 375°F and line a 12-muffin pan.
In a medium bowl, combine the dry ingredients, including 2 cups of the flour, all of the baking powder, and salt. Set this aside for now.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and sugar together on medium speed until light and fluffy (2-3 minutes). Then add the vanilla and eggs, one at a time, continuing to beat until creamy. After that, beat in the milk and Greek yogurt or sour cream.
Turn your mixer to low and add in the flour mixture, folding it in gently until it is just combined. Do not over-mix.
Toss the blueberries with the remaining 2 tsp of flour to evenly coat them. Add the blueberries to the batter and use a flexible spatula to fold them in.
Divide the batter evenly between the muffin cups, filling them to right about the top. Add a teaspoon of blueberry jam on top of each muffin and use a toothpick or fork to swirl it in. Bake for 23-27 minutes, or until muffins are cooked through. Best served warm. Enjoy!