About portobello mushrooms
Portobello mushrooms are fungi for people who want a meaty taste without the meat. This massive mushroom’s flavour is bold and earthy and just one is often all you’ll need per serving, such as in the burger recipe below.
Portobello mushrooms got their fancy, Italian-sounding name in the 1980s when mushrooms producers needed a more alluring name to help sell what is simple a fully mature brown, also called crimini, mushroom. The came up with portobello and its more exotic sounding name persuaded people to try them because they believed they were something special, which they indeed turned out to be.

Portobello Mushroom Burgers with Pesto Mayo and Asiago Cheese

Vegetarian burgers I like to serve with a green or Caesar salad.
Preparation time: 15 minutes
Cooking time: 5 minutes
Makes: 4 servings
4 large portobello mushrooms, about 5 inches (12 cm) in diameter
2 Tbsp (30 mL) olive oil
1 Tbsp (15 mL) fresh chopped rosemary (optional)
•    salt and freshly ground black pepper to taste
3/4 cup (175 mL) grated asiago cheese
4 to 8 slices ripe tomato
4 slices red onion
4 lettuce leafs
4 crusty buns, split and warmed
1/3 cup (75 mL) mayonnaise mixed with 2 Tbsp (30 mL)   pesto
Preheat an indoor or outdoor grill to medium-high. Remove the stem from each mushroom. (Stems can be saved and used to flavour stock if desired). Brush the mushrooms with the oil and sprinkle with rosemary, salt and pepper. Grill, starting cap-side down, 2 minutes per side, or until the mushrooms are tender. Reduce heat to low, top the mushrooms with cheese and cook until cheese melts. Spread the buns with the pesto-flavoured mayonnaise.  Set a lettuce leaf on each bottom bun. Set on the mushrooms, tomato, onion and top buns and serve.