Lightly cook the peas in boiling water, then drain and cool under the tap. Scatter them over a plate with the thinly sliced radishes and spring onion. Thin the crème fraîche to single cream consistency with a little milk and trickle it over the salad.
Snip over the cress and season with freshly ground black pepper. Serve with cold roast beef, adding some lime quarters to squeeze over.
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.