For the panzanella: Combine the vinegar, 1 cup water, the salt, sugar and garlic in a large jar or other container with a tight-fitting lid and shake, shake, shake to combine. Add the onions and cucumbers, shake again, and let sit for at least 1 hour. (You're making pickles here, and this step can totally be done ahead of time-like yesterday!)
Put the bread in a large bowl with 1/2 to 1 cup water to soften. Squeeze and knead the bread with your hands, and then let it sit for 30 minutes.
Squeeze out any excess water from the bread again, put the bread back in the bowl, and crumble it through your fingers. Toss in the tomatoes, add the pickled onions and cucumbers (strain these out and reserve the liquid), and stir to combine. Add the basil and some finishing oil; taste it to make sure it's delicious. Sprinkle in a few drops of the pickling liquid or a bit more oil if needed. Reserve.
For the blossoms: Wiggle your finger into the blossom down to the base, where the flower meets the stem, and carefully break off and remove the stamen (be gentle, you don't want to rip through the blossom while doing this). Repeat with all the blossoms.
In a medium bowl, combine the ricotta, Parmigiano and parsley and season with salt. Taste and re-season if needed. Put the ricotta mix into a pastry bag, carefully insert the tip of the bag into the flower and fill. Then gently close your hand around the flower to secure it. Place the stuffed blossom on a baking sheet and repeat with the remaining flowers.
Pour peanut oil into a large saucepan over medium-high heat; the oil should come 1 1/2 to 2 inches up the sides of the pan. While the oil heats, set up your drying situation next to the stove by putting a couple layers of paper towels on a baking sheet. To see if the oil is hot enough, drop a bit of flour into it. If it sizzles, you're good to go. If the oil begins to smoke, it's too hot, so reduce the heat.
Combine the flour and wine in a large bowl to make a very loose batter. Start with 3/4 cup of the wine and add more if needed.
Working in batches, dip each blossom in the batter to coat it, and then gently put each blossom in the oil, being careful not to overcrowd the pan. Let the blossoms cook until they turn color but stay nice and crispy on the outside, 1 to 2 minutes. Remove the blossoms from the oil with a slotted spoon or fish spatula, put them on the paper towels and immediately sprinkle with salt.
Divide the reserved panzanella among serving plates and top each with 2 crispy blossoms.