Preheat oven to 425 degrees F (220 degrees C). Line a baking sheet with aluminum foil.
Brush the lighter sides of the toast with olive oil. Place the toast pieces onto the prepared baking sheet with oiled sides down.
Spoon leftover creamed spinach onto the toast slices, spreading the spinach all the way to the edges. Top each with a sprinkle of Parmigiano-Reggiano cheese.
Bake in the preheated oven for 10 minutes. Turn on the oven's broiler and broil spinach toasts until the cheese is lightly browned, about 2 more minutes.
