Make the filling. In a bowl, add ricotta, egg, Parmesan cheese, lemon zest, chopped herb, salt and pepper. Mix everything together.
Use a resealable bag and open it up into a cup. This will help keep the filling in place. Spoon filling into the bag, making sure it's not too full. Close the bag, squeezing out as much air as you can and set aside.
Gently open up the squash blossom and remove the small stem from inside the flower, being careful not to tear the delicate petals. Leave the large stem intact, this will help when dipping the stuffed flower into the batter.
Fill the blossoms. Snip a small corner off the resealable bag and twist the large opening of the bag closed, creating a piping bag.
Open the squash flower and pipe the ricotta mixture into the flower opening, but not too much that it overflows. Gently twist the petals together and set aside. Repeat with the rest.
Heat a wide skillet with a ½ inch of vegetable oil (or any high-heat oil you like) to 375 degrees Fahrenheit. While the oil is heating up, make the coating.
In another bowl, add flour, salt and pepper and sparkling water. Whisk together until it looks like a pancake batter consistency.
Dredge the stuffed blossoms. Use the stem to dip the blossom into the batter. Allow excess batter to drip off. Gently drop the stuffed squash blossom into the hot oil. It should sizzle right away.
Fry the squash flowers on the first side for about 2-3 minutes until lightly golden brown and carefully flip to other side and fry for another 1-2 minutes until puffed up and lightly golden brown.
Place fried squash blossoms onto paper towel lined plate and immediately season with flaky salt on top. Serve immediately with a squeeze of fresh lemon juice.