In a large mixing bowl, combine the ricotta cheese, flour, semolina, eggs, sugar, baking powder, vanilla extract, and salt. Mix until well combined. The dough should be slightly sticky but manageable.
Divide the dough into small portions and shape each portion into a ball. Use your thumb to make an indentation in the center of each ball to form a small well. This will help create the classic Papanasi shape.
Heat a large pot of vegetable oil over medium heat. The oil should be deep enough to submerge the dough balls.
Carefully drop the dough balls into the hot oil, working in batches if necessary. Fry the Papanasi for about 3-4 minutes on each side, or until golden brown and cooked through.
Use a slotted spoon to transfer the Papanasi to a plate lined with paper towels to drain excess oil.
In a small bowl, mix together the sour cream, sugar, and vanilla extract until smooth.
Place the fried Papanasi on a serving plate. Top with a dollop of the sweetened sour cream and a spoonful of fruit preserves or jam.
Optionally, dust with powdered sugar before serving.
Enjoy your meal!