Great to serve the crostini on small plates with the drisee salad or can be served as passed appetizers topped with a sprig of dressed frisee.
Preheat oven to 400°F. Arrange bread slices on baking sheet. Brush bread slices on top side with 2 tablespoons walnut oil. Bake until crisp, about 5 minutes.
Mix walnuts, cheese, 4 tablespoons shallots, and dried cranberries in medium bowl. Spread mixture on toasts. Bake until cheese melts, about 4 minutes.
Meanwhile, combine frisée, 2 tablespoons shallots, 2 tablespoons walnut oil, and vinegar in bowl. Sprinkle with fleur de sel; toss. Serve with crostini.