Begin by pre-heating the oven to 375°F (190°C) and greasing your 9-inch springform pan. In a medium bowl, stir together flour, half the sugar, and baking powder. Use a pastry blender (or finger-pinch) to cut in the butter until the mixture resembles coarse crumbs. Add the whole egg and 1 teaspoon vanilla extract, then press the batter into the bottom of the prepared pan and scatter the fresh blueberries evenly over the top.
In a separate bowl, whisk together the sour cream, the remaining ½ cup sugar, the egg yolks and the last teaspoon of vanilla. Pour this creamy mixture gently over the blueberries in the pan, ensuring it spreads to the edges and covers them completely.
Place the pan in the pre-heated oven and bake until the top is light golden-brown and the center is set (about 60 to 70 minutes). After removing it from the oven, allow it to cool on a wire rack. Then run a knife around the edge of the pan, remove the outer ring, and chill in the fridge if you prefer it firmer before serving.