Peel and finely dice the shallots. Wash lime hot, grate dry, halve fruit. Squeeze juice from one half, cut the remaining half into slices. Pick cheese and ham. Cut avocados in half, remove seeds and scrape out some of the fruit flesh with a spoon.
Mix shallots, ham, cheese and pulp, season with salt, pepper and lime juice. Arrange in the avocado halves and drizzle with oil. Garnish with marjoram.