Place a slice of bread on a rack. Butter the bread if you like.
Using a heart-shape cookie cutter, cut a hole out of the other bread, leaving around 1 cm border. Cut the slice of cheese into 4 strips and lay them as close as the edges of the bread as possible. Lay the bread-with-a-hole on top and then crack the egg inside.
Sprinkle with a little salt and black pepper. Drop in a dot of butter if you like. Bake for 15 for runny yolk; 20 minutes for almost fully-cooked yolk.
NOTES
I baked mine for 20 minutes, and the egg is almost cooked. Because I love runny yolks, I'm gonna bake mine for 15 minutes the next time I make it again.
Use any cookie cutter you can find, as long as the hole is big enough so that the whole egg fits into the hole.
If using big eggs, some of the egg whites may flow out, but doesn't matter as it'll all be absorbed by the bread during baking.