Drain the ricotta. Wrap the ricotta cheese in a cheese cloth, then place in a colander set over a large bowl. Weigh the ricotta down with something heavy to press out excess water. Allow to drain for 8 hours or overnight. Skipping this step will result in the gnudi falling apart during cooking.
Make the gnudi mixture. In a large bowl, combine drained ricotta, ¼ cup Pecorino Romano, ¼ cup flour, 1 large egg yolk, 1 tsp Kosher salt, and ¼ tsp black pepper. Use a spatula to thoroughly mix. Transfer the bowl to a fridge to chill for 1 hour.
Prepare a baking sheet. Line a rimmed sheet pan with parchment paper, then dust with about ¼ cup of flour.
Form the gnudi. Divide the mixture into thirds, then roll each portion into a log about 10-12 inches long and 1-inch in diameter. Use a bench scraper to cut the gnudi into 1-inch long pieces, yielding about 10 gnudi per rope. With lightly floured hands, gently roll each gnudi into a uniform ball, then place onto the flour lined baking sheet. Repeat with remaining gnudi.
Chill before cooking. Dust the remaining ¼ cup of flour on top of the formed gnudi, ensuring they’re evenly coated on all sides. Transfer the prepared gnudi to a refrigerator to chill for at least 30 minutes.
Blanch the vegetables. While the gnudi are chilling, bring a large pot of water to a boil, then season generously with Kosher salt, about 2-3 Tbsp. Add the asparagus and peas, then cook for 3 minutes. Use a slotted spoon or spider to transfer to an ice bath to stop the cooking process. After a few minutes, drain and pat dry. Bring the water back up to a simmer to cook the gnudi.
Prepare the sauce. Melt 4 Tbsp butter in a large skillet over medium heat until it turns golden brown, about 4 minutes. Add 2 sprigs of sage leaves, if using, then cook until the sage stops sizzling, about 30 seconds. Remove the sage. Add the blanched asparagus and peas, then season lightly with Kosher salt. Lower the heat until the gnudi are cooked.
Cook the gnudi. Carefully lower the gnudi into the simmering water, then cook until they float to the surface, about 2-3 minutes. Use a slotted spoon to immediately transfer the gnudi to the prepared sauce. Do not discard cooking water.
Finish in the sauce. Sauté the gnudi in the sauce for about 2 minutes over medium-high heat, adding about ½ cup of reserved cooking water and swirling the pan gently to coat the gnudi without breaking them. Spoon a few of the gnudi onto individual plates, drizzling more of the sauce on top, as wanted, then serve immediately with a drizzle of olive oil, grated Parmesan, lemon zest, additional freshly ground black pepper, and a pinch of flaky sea salt.