A few years ago my friend made some fantastic portabellas that still make my mouth water today. I haven't had much success in the past with them, until now. The key is to marinate them prior to cooking, and not to overcook! Who knew?
big portabellas, one for each person
teriyaki marinade or sauce
1 Tbsp. finely shredded ginger
Your favorite fixin's for burgers
Marinate the portabellas in a healthy mix of olive oil and teriyaki sauce (with the ginger) for about 30 minutes. Then oil a frying pan (I used a cast iron one) and saute until the bellas are carmelized on top, about 2 minutes or so. Don't overcook and don't push them down (they'll break, as you can see by my photo below).
Then flip and repeat on the other side. Top with your favorite burger toppings and you're good to go!