Mushroom Onion and Spinach Sandwich

"Last month I went for brunch with friends and there we had delicious sandwich which consisted of caramelised onion, sautéed mushroom and goat cheese. So I thought of recreating the same sandwich, with a healthier touch. So make this sandwich healthy, I have used whole grain bread instead of regular white bread, also added some spinach which enhances the taste and a great way to eat more veggies."