Chef John's Simple Spinach Toasts

Ingredients (4)

• + 4 thick slices bread, toasted add to pantry
• + 1 tablespoon olive oil, divided add to pantry
• ✓ 1 ½ cups leftover creamed spinach, divided
• + 1 tablespoon freshly shredded Parmigiano-Reggiano cheese, divided add to pantry