Cook chicken fillet on the grill or in a frying pan or in a roaster. Cook mixed vegetables for about 15min, then set aside to cool. Mix gruyere cheese with smoked ham steak and chicken. Mix yogurt with mayonnaise and pour sauce over it. In a food processor whisk egg, mustard and sugar. Add sunflower oil and lemon juice gradually in 4-5 increments.
NOTE: If the mayonnaise becomes too thick add oil to thin it out; if the opposite, add lemon juice. Bon appétit!!!