Toast the bread and if using cheese, melt the cheese on top.
Mash the avocado and spread it onto a plate. Using a Christmas tree cookie cutter (or a knife), cut the avocado into a Christmas tree shape. Using a spatula (or two), carefully slide the avocado onto the spatulas, then transfer it onto the toast.
Cut a small star out of cheese and place it at the top of the tree. Drizzle the tree with olive oil (for popcorn tinsel) and Everything But the Bagel (for ornaments and lights). Enjoy!