This is a salad where the vegetables really shine and the lettuce plays a supporting role. It requires a bit of work up front to blanch all the veg, but the results are impressive.
To prepare vinaigrette: Whisk lemon juice, egg yolk, whole-grain and Dijon mustard, shallot, garlic and 1/2 teaspoon salt in a medium bowl. Slowly stream in oil while whisking until creamy and emulsified. Refrigerate until ready to use.
To prepare salad: Place a large bowl of ice water by the stove. Bring a large pot of water to a boil over high heat and add salt. Add potatoes and reduce heat to a gentle simmer. Cook until the potatoes are tender when pierced with the tip of a knife but not falling apart, 12 to 15 minutes. With a slotted spoon, immediately transfer the potatoes to the ice bath. Return the water to a boil and blanch broccolini, asparagus and peas in separate batches until tender-crisp, 1 to 3 minutes. Transfer each to the ice bath. Drain the vegetables and pat dry. Cut into bite-size pieces.
Arrange the blanched vegetables, lettuce and radishes in a shallow bowl or platter. Drizzle with 1/2 cup dressing (reserve the remaining dressing for another use) and sprinkle with Gouda, almonds and pepper.
To make ahead: Refrigerate vinaigrette (Step 1) for up to 3 days.
Tip: When a recipe calls for raw eggs, you can minimize the risk of foodborne illness by using pasteurized-in-the-shell eggs. Look for them in the refrigerator case near other whole eggs.