Slice onions and saute over medium-high heat in 1 Tbl of margarine/vegan margarine plus 1-1/2 tsp of oil and sugar until tender and translucent. Season with salt and pepper.
Add the wine, worcestershire/vegan worcestershire and vegetable or mushroom broth. Cook down until the liquid is almost all evaporated.
Remove the onions and add 1 Tbl of margarine/vegan margarine to the same pan. Add the prepared mushroom caps and toss well to coat. Cook for a few minutes until just starting to get tender.
Preheat the oven to 325 degrees.
Arrange the mushrooms, cap side down and season with salt.
Fill each with a generous spoonful of onions and top with cheese/vegan cheese shreds.
Lastly, top with chopped parsley.
Bake uncovered for 10-15 minutes or until fork tender. Don't overcook, you still want to have some "bite" to them.
Season with a pinch more salt if desired and serve immediately.