Cook the green beans in boiling water for 5 minutes. Drain and refresh with cold water to stop them from cooking further, then roughly chop and set aside. Meanwhile, place the bacon under a preheated medium grill for 3–4 minutes until golden and cooked. Cool slightly, then snip roughly with scissors. Toss the green beans and bacon with the peas.
Beat the eggs with the mustard and paprika. Heat the oil in a medium nonstick frying pan with a metal handle, then pour in the eggs. Working quickly, scatter over the beans, peas and bacon. Cook over a gentle heat until the base has set.
Sprinkle over the Parmesan and place the pan under the grill for 2–3 minutes until the frittata is set and golden.
Cut the frittata into wedges. If not serving immediately, wrap it in foil to keep warm.