To make the pea puree, place the shelled peas, water, lemon zest, lemon juice, sugar, olive oil, salt, and pepper in a food processor or blender and process until smooth. The puree can be made a day ahead of time, if desired. Divide the pea puree among 4 large plates and smooth out with a spoon or offset spatula. Set aside.
To make the dressing, combine in a small bowl the mustard, vinegar, sugar, salt, and pepper, then whisk in the olive oil to incorporate.
To make the salad, divide the corn among the 4 plates with the pea puree and top with the sugar snap peas, pea tendrils, radicchio, and herbs. Drizzle with the dressing, sprinkle with the ricotta salata, and garnish with the edible flowers if desired.
Serve immediately.