Bacon, Cheddar, Spinach, and Mushroom "Grilled" Flatbread Sandwich

YOU. GUYS. This sandwich. Oh. Dear. God.

It began as many things in my kitchen do--with a semi-specific craving: I wanted a mushroom grilled cheese sandwich. It's gray and chilly outside, and I wanted to bring some warmth inside! This sandwich did exactly that--and filled the house with delicious aromas to boot!