Place a small skillet over low heat; add the butter, EVOO and the garlic clove. Let the garlic infuse into the EVOO for a couple minutes, or until you smell the garlic.
Meanwhile, in a small bowl, mix together the ricotta cheese, spinach, Parmigiano Reggiano cheese, salt, pepper and nutmeg, until combined.
Lightly brush one side of each slice of bread with the garlic butter. On one slice of bread, on the unbuttered side, place a slice of provolone and a good slather of the ricotta mixture. On the other slice of bread, also on the unbuttered side, place the mozzarella. Close the sandwich.
Place a small skillet over medium heat and place the sandwich in the pan. Cook until golden brown, about 3-4 minutes per side. Flip and cook until the cheese is melted and the other side is golden brown.