In a large mixing bowl, combine the cottage cheese and Dijon mustard, stirring until the mixture is cohesive.
Add the diced chicken, halved grapes, and sliced green onions to the bowl.
Stir the ingredients gently until the chicken is thoroughly coated with the cottage cheese mixture.
Fold in the toasted slivered almonds immediately before assembly to ensure they remain crisp.
Season the salad with sea salt and black pepper to taste.
Place a leaf of butter lettuce on two slices of the whole grain bread.
Distribute the chicken salad evenly over the lettuce and top with the remaining bread slices.
Cut diagonally and serve immediately.