Heat a medium pan over medium-high heat. Add the pine nuts and cook for 4 minutes, until lightly browned, stirring. Remove from heat and set aside.
Pour the sparkling water in a medium bowl. Whisk in the flour until combined. Set aside.
Put the pine nuts, basil, garlic and sea salt and olive oil in a food processor with the metal blade attached and process until combined. Transfer to a medium bowl. Add the fontina, ricotta, and lemon juice. Season with salt and pepper and stir until combined.
Carefully, spoon the mixture inside of each squash blossom and twist them closed at the top. Brush each squash blossom with the batter, making sure to lightly coat all sides.
Heat the olive oil in a large pan. Working in batches, add the squash blossoms to the pan and fry them on both sides, about 2-3 minutes total. Transfer them to paper towels and then place them on a serving piece of your choice. Sprinkle sea salt over the top and serve immediately with lemon wedges.