Turn oven broiler on low, position oven rack in the top 1/3 of oven, and line a baking sheet with aluminum foil.
Place ciabatta slices, cut side up, on baking sheet and place in oven.
Bake bread for 2 – 3 minutes, or until crisped: remove and set aside.
Drain liquids from tuna cans and pour tuna into a large bowl.
Add mayonnaise or yogurt to the bowl, along with chopped parsley, and mix everything together until blended completely.
Mix in corn kernels and shallot until coated and integrated.
Evenly divide tuna mixture and spread it out onto toasted ciabatta rolls and top each slice with 2 slices of cheddar cheese.
Optional: sprinkle each slice with a pinch of nutmeg.
Return rolls to oven and cook for 4 – 5 minutes, or until cheese is melted and tuna heated through.
Remove from oven and serve immediately.
