Pile the lettuce onto a large platter or a salad bowl.
If using defrosted frozen peas or fresh peas that are sweet and tender, scatter them over the lettuce. If the peas are a bit starchy, blanch in a pot of salted boiling water until just tender, 2 to 3 minutes. Drain peas, and immerse in ice water, then drain and scatter over the lettuce.
Cut the asparagus and snap peas on a diagonal into very thin slices. You should have about 1 cup of each. Cut the radishes into paper thin slices (use a mandolin if you have one). Scatter the asparagus, snap peas, radishes, and mint over the lettuce.
To make the dressing, whisk together the sour cream, olive oil, lemon juice, lemon zest, chives, mustard, and salt in a small bowl.
Drizzle about two-thirds of the dressing over the salad, toss well. Add more dressing if needed and toss again (you may have some leftover dressing). Taste and season with fresh ground black pepper and salt, if needed. Garnish with toasted almonds. Serve immediately.