Heat oil in a large pan and add the spinach and garlic and cook for about 30 seconds or until it begins to wilt. Remove from heat and set aside.
Add some earth balance vegan butter to the pan and melt over medium low heat. Then add the slices of bread and light toast on one side. 1 minute.
Remove from the heat and on one piece of the toasted side, add the cheese and on the other layer the spinach, tomato, onion and basil.
Melt some more butter in the pan and add the two slices of bread. Over medium low heat start to toast the other side and melt the cheese. Cover the pan with a lid for 1 minute if needed to help the cheese start to melt. After 1 more minute, place the cheese on top of the other half sandwich and press down with a spatula. Flip and toast for another 30 seconds to a minute.
Slice in half and serve!