In a blender, combine cottage cheese, egg yolks, salt and pepper and Aji or Tabasco. With motor running, add oil in a slow stream, blending until incorporated. Add lemon juice, milk and scallions and blend until combined. (For a thicker sauce, add more cottage cheese, for a thinner sauce, add more milk.)
Line plates with lettuce leaves. Toss potatoes with sauce to coat evenly and arrange on lettuce leaves. Top with egg slices and place black olives around the edges of the plates.
c.1996, M.S. Milliken & S. Feniger, all rights reserved