Preheat a nonstick frying pan on medium-low for a minute or two.

Place both frozen slices of bread down on the hot pan. Cook for 2 minutes without moving.

Flip the slices and top each warm side with the cheese (this will help all of the cheese melt evenly). Don’t cover them with the other slices of bread yet.

Cook for 2 minutes open-faced, keeping the heat on medium-low. Lower the heat if it starts to sizzle.

Using tongs or a spatula, carefully lift one side and place cheese-side down on top of the other, so the two open-faces are now together into one sandwich. Press down lightly with spatula.

Cook for a final 2 minutes.

Transfer to a cutting board and cut, if desired.

Serve immediately.