In a medium pot, heat the stock and the lemon peel over medium-low. Cover and keep warm.
In a round-bottom pan or large skillet, heat the olive oil, two turns of the pan, over medium-high. Add the shallots and garlic and stir until softened, about 5 minutes. Add the rice; stir until coated, about 1 minute. Season with salt and pepper. Add the wine; stir until evaporated, about 2 minutes. Add about 2 cups warm stock and cook, stirring frequently, until almost evaporated, about 6 minutes. Add 2 more cups stock and cook, stirring frequently, until almost evaporated, about 6 minutes more. Add 1 cup stock and the lemon zest; stir until almost evaporated, about 3 minutes. Taste the rice. If it's tender but still has a bite to it, stir in the lemon juice, mascarpone and 1 cup Parmigiano-Reggiano. Season and stir in some of the remaining stock if the risotto isn't saucy enough. Divide among bowls; garnish with basil and more grated cheese.