Add drained spinach, gently incorporating into the onion and garlic and cook until any liquid from the spinach has evaporated - just a couple of minutes are needed.
Stir in crumbled feta, sprinkle with dried dill and remove from heat.
Heat your grill.
Paint one side of each of five slices of bread with mayonnaise or softened butter and place mayo-side-down on the grill.
Place one slice of provolone on each.
Scoop the spinach mixture evenly on top of each cheese slice.
Top spinach mixture with remaining provolone.
Place remaining bread slices over each painting with mayo or bitter.
When golden brown, flip and grill the reverse side.
Let sit for a couple of minutes before slicing
Recipe by SEA SALT GALLEY KAT at https://www.seasaltgalleykat.com/sandwiches/spanakopita-grilled-cheese/