The shallot vinaigrette can be refrigerated for up to 5 days. The red onions can be roasted and the steak can be grilled 1 day ahead. Refrigerate and bring to room temperature, then slice the steak before serving.
Grilled Chili-Steak Salad Sandwich Variation: Prepare the recipe through Step 5 and toss the frisee with the parsley, roasted onions and 1/2 cup of the vinaigrette. Grill 12 slices of country bread. Arrange tomato slices on half of the grilled bread and top with the frisee salad and blue cheese. Layer the grilled steak over the salad, close the sandwiches and serve.