1. Make the Blueberry Filling:

1. In a small saucepan over medium heat, combine the blueberries, sugar, 3 tablespoons of water, and lemon juice.
2. Stir occasionally and bring the mixture to a boil.
3. Continue to cook for 3-4 minutes after it comes to a boil, or until the blueberries have burst and released their juices.
4. In a small bowl, whisk together the remaining 4 tablespoons of water and the cornstarch to create a slurry.
5. Add the cornstarch slurry to the blueberry mixture.
6. Stir constantly until the mixture thickens (about 1-2 minutes).
7. Remove from heat and let the filling cool completely.

2. Make the Cream Cheese Filling:

1. In a medium bowl, using an electric mixer, beat the softened cream cheese until light and fluffy (about 2-3 minutes).
2. Add the sugar, vanilla extract, and lemon juice.
3. Beat for another 2 minutes, or until well combined and smooth.

3. Assemble the Egg Rolls:

1. Lay an egg roll wrapper on a clean, dry surface, with one corner pointing towards you (like a diamond).
2. Place about 2 tablespoons of the cream cheese filling in the center of the wrapper.
3. Top the cream cheese filling with 1-2 tablespoons of the cooled blueberry filling. Do not overfill, or the egg rolls will be difficult to seal.
4. Moisten the edges of the egg roll wrapper with water. This helps create a seal.
5. Fold the bottom corner over the filling.
6. Fold in the two side corners.
7. Tightly roll the egg roll from the bottom up, sealing the top corner. Make sure the egg roll is sealed tightly to prevent the filling from leaking out during frying.
8. Repeat with the remaining egg roll wrappers and filling.

4. Fry the Egg Rolls:

1. Heat the vegetable oil in a large skillet or frying pan over medium heat. The oil should be about 375°F (190°C). If you don’t have a thermometer, you can test the oil by dropping a small piece of egg roll wrapper into it; it should sizzle immediately.
2. Carefully add the egg rolls to the hot oil, a few at a time, making sure not to overcrowd the pan.
3. Fry for 2-3 minutes per side, or until golden brown and crispy.
4. Use tongs or a slotted spoon to transfer the cooked egg rolls to a paper towel-lined plate to drain excess oil.

5. Serve:

1. Dust the warm egg rolls with powdered sugar.
2. Serve immediately.