How to make
Boil the orzo according to package directions in salted water. Strain it in a strainer.
Cut the crab rolls into round circles. Thaw the mussels if they've been frozen.
Put the boiled orzo, crab rolls, mussels and the olives, cut into slices, in a bowl.
In another bowl, pour in the mayonnaise, add the mustard, lemon, salt, black pepper, stir everything well until homogeneous.
Pour the resulting sauce in the bowl with the other ingredients and stir well. Optionally, decorate with any ingredients you have available.