In a small pot, heat the stock over low.
In a round-bottom pot or pan, heat 1 tbsp. oil, one turn of the pan, over medium-high. Add the shallots and garlic; cook, stirring often, until tender, 2 to 3 minutes. Add the rice and season with salt and pepper. Cook, stirring constantly, until the rice is coated, about a minute. Add the wine, thyme and zest. Cook, stirring often, until the rice absorbs the wine, about 2 minutes. Start adding the stock, a couple of ladles at a time, stirring vigorously with a wooden spoon after each addition. Let the rice absorb the stock between additions. From the time you start adding the stock, the dish should take exactly 18 minutes for the rice to be al dente. You will use all 6 cups of the stock.
In a food processor, pulse half the peas with the parsley until finely chopped; season with salt.
Chop half the shrimp into small pieces.
In a small skillet, heat the remaining 1 tbsp. oil, one turn of the pan, over medium-high. Add the whole shrimp and cook, tossing often, until pink and firm, about 2 minutes; season.
During the last 3 minutes of cooking the risotto, add the finely chopped pea mixture, the whole peas and the chopped shrimp. Add the butter and cheese. Cook, stirring often, until the shrimp is pink and firm and the risotto is creamy. Stir in the lemon juice.
Serve the risotto in shallow bowls topped with the cooked whole shrimp.