Treat portobellos like meat.
Yes, but you have to cook them right or you’ll end up with a soggy, flavorless disk.
The biggest mistake people make is treating mushrooms like delicate vegetables. Portobellos are dense and spongy—they need high, direct heat and time to dry out and concentrate flavor. A gas grill or charcoal chimney works best.
Do these three things:
- Remove the gills. They hold moisture and turn slimy. Just scrape them out with a spoon.
- Marinate, but keep it simple. Olive oil, balsamic, salt, pepper, maybe a smashed garlic clove. 20 minutes max. Any longer and they get waterlogged.
- Grill stem-down first. 5-7 minutes each side over medium-high heat. You want grill marks and some char. Mushrooms are done when they’re tender but still have structure.
Don’t bother with cheese unless it’s firmly melted on. A slice of provolone or smoked gouda works. And please toast the bun.
They’re not a substitute for beef—they’re their own thing. Treat them that way and they’ll hold up.