For the rice, in a medium saucepan, heat the oil, one turn of the pan, over medium to medium-high. Add the butter. When it stops foaming, add the onion and garlic and cook, stirring often, until softened, 2 to 3 minutes. Add the pasta and cook, stirring often, until deep golden and fragrant, about 6 minutes. Add the rice and cook until toasted, about 1 minute more; season with salt and pepper. Stir in the smoked paprika. Add the stock and bring to a boil. Reduce heat to low. Cover and simmer until the rice is almost tender, about 15 minutes. Stir in the peas and pimientos. Cover and cook until the rice is tender, about 5 minutes. Fluff the rice with a fork.
For the shrimp, in a large nonstick skillet, heat the oil, two turns of the pan, over medium-high to high. Add the shrimp and cook until just opaque in the centers, about 2 minutes per side. Add the spring onions and garlic; season with salt and pepper. Add the crushed red pepper and toss for 2 to 3 minutes more. Mix in the sherry; cook until almost completely reduced, about 1 minute. Add the lemon juice and butter. Swirl the skillet until the butter melts, about 1 minute. Top with the parsley and hot sauce. Divide the rice among shallow bowls. Top with the shrimp.