Preheat the oven to 400 degrees F. Simmer the chicken stock in a medium saucepan.
In a 13-inch paella pan, heat the olive oil over medium-high heat. Add the chorizo and cook until lightly browned; transfer to a paper-towel-lined plate. Add the onions, peppers and garlic to the pan and cook until softened, about 5 minutes. Add the tomatoes and stir to combine, then stir in the rice and saffron. Deglaze the pan with the white wine and cook, stirring, until most of the liquid has evaporated, 2 minutes. Pour in 5 cups of the simmering chicken stock and bring to a boil over high heat, stirring constantly. Immediately remove the pan from the heat and season with salt. Arrange the chorizo and shrimp on top of the rice.
Set the pan on the floor of the oven or on the lowest oven rack and bake, uncovered, for 20 minutes. (Do not stir the paella once it goes in the oven.) Scatter the peas over the paella, return to the oven and continue cooking until all the liquid has been absorbed and the rice is tender but not too soft, another 5 to 10 minutes. If the rice needs further cooking, add the remaining cup of stock and cook for an additional 5 to 10 minutes.
Let the paella stand at room temperature, covered with foil, for 5 minutes. Serve garnished with lemon wedges and parsley.