These hearty Portobello Vegetable Stacks are wonderful to serve with barbecued steak, lamb chops or pork chops. I have also used them as an entree for a vegetarian meal.
Some people may prefer to use raw onion, instead of the caramelized onions, but I have to say that the caramelizing adds a unique flavour to these stacks. Because balsamic vinegar is also sweet, I sometimes omit the brown sugar when caramelizing the onions.
The caramelized onion recipe below uses 3 onions, but can easily be adapted for more onions. They will keep in the fridge for several days. They can also be used as an appetizer when served on a slightly warmed Camembert cheese.
Enjoy!

Portobello Veggie Stacks
Ingredients
- 4 portobello mushrooms - stems removed and lightly brushed with olive oil – top and bottom
- 6 bocconcini balls - sliced into 1/4 inch slices
- 2 tomatoes - sliced into 1/2 inch slices or large chop
- 2 basil leaves - chopped, or a sprinkle of dried basil, if fresh is unavailable
- 1/2 cup Asiago cheese - grated
Caramelized Onions
- 3 onions - medium chop
- 2 tbsp olive oil
- 1 tbsp brown sugar
- 2 tsp balsamic vinegar
- 1 pinch salt and pepper
Instructions
Caramelized Onions
- Heat oil in large frying pan on medium-high, add onions; cook until wilted and starting to brown, about 5-10 minutes, being careful not to burn (stir throughout, turn heat down if starting to brown too much)
- Add sugar, vinegar, salt, and pepper. Reduce heat to medium-low; cook for 15-25 minutes until onions are caramelized and golden.
Portobello Stacks
- Preheat oven to 350 ℉ (175 ℃).
- Assemble the stacks by layering one portabello mushroom, caramelized onion, bocconcini, basil, and tomato. Sprinkle with grated asiago.
- Place stacks on a cookie sheet (with edges, as the stack can get a little runny) or in a rectangular Pyrex dish covered with parchment paper. The dish needs to be large enough to hold the stacks in one layer, not touching.

- Bake about 20-25 minutes, until the cheese melts and the veggies soften.
