Sauté onions in olive oil over low heat. This will take about 30 minutes until they are a deep caramel colour. Stir often checking if they need more oil to keep from burning. Season with salt and pepper and add a teaspoon of sugar if you like to help them deepen in colour.
Add the mushrooms about 30 minutes in and let them soften another 10 minutes.
Wipe out the pan and keep over low heat.
Spread some of the onion/mushrooms on ONE SIDE only and top with some baby spinach leaves.
Place in the pan and let it crisp up (1 min or 2) then fold the tortilla/wrap in half.
Cut in 2 and serve.
Note: Can add any type of cheese you like too. Feta is yum with this.