Season chicken breasts with salt and pepper; grill over medium-high heat until the internal temperature reaches 74°C (165°F), then rest and slice.
Boil eggs for 9 minutes, immediately transfer to an ice bath, peel, and quarter.
Blanch the asparagus and snap peas in boiling water for 120 seconds, then shock in ice water to maintain color and texture.
Prepare the dressing by whisking olive oil, lemon juice, Dijon mustard, salt, and pepper until emulsified.
Layer the chopped romaine lettuce as a base on a large serving platter.
Arrange the grilled chicken, boiled eggs, asparagus, snap peas, avocado, and cucumber in distinct parallel rows across the lettuce.
Garnish the salad with crumbled feta cheese and pumpkin seeds.
Drizzle the lemon-mustard vinaigrette over the salad components immediately before serving.