1. In a saucepan, combine the fresh blueberries, sugar, lemon juice, and 4 tablespoons of water.

2. Cook over medium heat, stirring gently, until the blueberries burst and release their juices, about 5-7 minutes.

3. In a small bowl, mix the remaining 3 tablespoons of water with cornstarch until smooth.

4. Add this cornstarch mixture to the blueberry sauce, stirring continuously, and cook until thickened, approximately 2-3 minutes.

5. Remove from heat and let cool completely.

6. In a mixing bowl, beat together the cream cheese, sugar, lemon juice, and vanilla extract until the mixture is light and fluffy, about 3-4 minutes.

7. Lay out an egg roll wrapper on a clean surface, with one corner facing you (like a diamond).

8. Spread a layer of the cream cheese mixture in the center of the wrapper, followed by a spoonful of the blueberry filling.

9. Moisten the edges of the wrapper with a little water.

10. Fold the sides over the filling, then roll up tightly from the bottom to the top, sealing the edges as you go. Repeat with the remaining wrappers and fillings.

11. In a deep skillet or fryer, heat the vegetable oil to 350°F (175°C).

12. Fry the egg rolls in batches, cooking until they are golden brown and crispy, about 2-3 minutes per side.

13. Drain on paper towels and dust with powdered sugar before serving.