Drain the cans of tuna into a fine sieve with a bowl underneath, gently flake the tuna to remove any of the excess oil, then transfer the tuna into a large bowl, along with the Greek yogurt, dijon mustard, chopped red onion, chopped dill pickles, chopped chives, grated garlic, lemon juice, and season with sea salt and a generous portion of black pepper, mix together until well mixed, add in more yogurt if the mixture is too dry

Thinly slice the cucumber

Lightly toast the slices of sandwich bread

Add the tuna salad over the slices of toast, top off with some slices of cucumber, and another slice of toast, enjoy!