One could be forgiven for thinking that vegetarians are made up of avocados, which have appeared on menus everywhere, and not just as guacamole. Nothing says fresh and healthy like a fan of avocado slices on top of a salad, or nestled next to the kale on your grain bowl. Avocado toast is now as easy to find as hot cereal on restaurant menus, and you might see it floating in a chilled soup, as the weather warms up.

There's actually an all-avocado restaurant in Brooklyn now, so we may have hit hipster peak.

But where the avocado has really made a stand is in the sandwich, that space between two slices of bread that was once the territory of sliced meats and cheeses, tomatoes and lettuce. Why has the green fruit suddenly become an option for sandwich stuffing?

I think we can thank the vegans. When you are making a sandwich without cheese, you need something moist and creamy to take its place. In a grilled sandwich, you need to replace the melting cheese that held it all together.

Enter the avocado. A bit of avocado is like nature's mayonnaise, schmeared on the bread. But if you mash it and use it in place of the melty cheese, it's nature's Brie. Suddenly you have a luscious, bright green bit of plant-based magic happening.

I used my panini grill to make this satisfying sandwich, but you can make it easily without one. It won't have the snazzy grill marks, but you'll get the point across. I like using the panini grill to grill some veggies to put in the sandwich, then grill the whole sandwich, making good use of the appliance.

A quick, thick pesto creates a creamy herbal layer on one slice of bread, and the mashed avocado coats the other slice. The two provide delicious binders for the veggies in between.

Grilled shiitake mushrooms shrink and become meaty and chewy, and shredded carrots add crunch. Plump sun-dried tomatoes give a bit of that sweet and tart flavor, without all the juiciness of a fresh tomato. A tangle of cooked spinach gives the sandwich a bit of vegetable heft, and is a classic Panini filling.

If this sandwich isn't loaded enough for you, you can always put a slice of cheese on it. But you don't need it. Sometimes those hipsters are right.

Robin Asbell is a cooking instructor and author of "Big Vegan," "The Whole Grain Promise" and "Great Bowls of Food." Find her at