Green Leaf Lettuce with Radishes and Spring Onions

Name: Green Leaf Lettuce with Radishes and Spring Onions
Ingredients: For the vinaigrette:; 1 tablespoon minced spring onion; 1 tablespoon freshly squeezed lemon juice, plus more to taste; 1/2 teaspoon medium-grain German mustard; 1/4 teaspoon sea salt; 2 tablespoons extra-virgin olive oil; For the salad:; 1 bunch radishes, leaves trimmed to 1/4 inch and quartered; sea salt; 1 bunch green leaf lettuce, torn, any thick stems removed; 3 spring onions, minced (if there are flowers, halve them and reserve for garnish); ground black pepper