Mix all ingredients together, except for bread, butter and cheese.
Thinly and evenly spread softened butter on slices of bread, on both sides. Or melt butter and brush on.
Place 2 pieces of bread, buttered side down in a frying pan over medium heat. Toast on first side and then flip to second side.
Top bread with 2 slices cheese, then top cheese with 1/4 of the tuna mixture.
Place second piece of bread on top of the sandwich, with buttered side up, toasted side towards tuna. Place sandwiches in a large non-stick skillet over medium heat. Top pan with lid so that cheese melts nicely.
When sandwiches are golden brown, carefully flip with spatula, so you don't lose ingredients. Be careful not to burn the bread.
Repeat until you have 4 sandwiches.
Let cool slightly before serving.
Can be kept warm in the oven on low heat, until all sandwiches are toasted.
Video
Notes
When you hear the sizzling stop in the pan, it indicates that the sandwich is ready to flip.Best if eaten fresh.Tuna can be refrigerated 1 day.Do not freeze.See post above for bread and accompaniment suggestions.