All amounts are approximate. This recipe allows for creativity.

4 Tb olive oil
4 Tb balsamic or red wine vinegar
3 fresh rosemary sprigs or 1 1/2 tsp dried
3 fresh thyme sprigs or 1 1/2 tsp dried
6 cups assorted mushrooms. I use about 1 lb button, 1/4 lb shiitake and 1/4 lb portabello. All cut into large, bite size pieces.
salt and pepper
1 Tb beef stock concentrate paste (I use "Better than Bullion")
1 1/4 cup water
1/4 cup Marsala or other sweet wine
2 Tb butter
1 tsp flour
1 cup roasted peeled garlic, coarsely chopped*

Preheat oven to 425°. Line a baking sheet with foil, or spray with oil spray. Combine olive oil, vinegar, rosemary and thyme. Put mushrooms in a large bowl and cover them with the marinade and stir until coated. Season with salt and pepper and toss. Arrange on baking sheet and roast until brown, tender and a little crisp around edges, about 25 minutes.

While baking, make sauce. Combine stock concentrate, water and Marsala in saucepan and bring to boil, stirring to dissolve concentrate.   Boil down until reduced to almost half. Add butter and stir to melt.   Take a couple TB of liquid out of pan and put into small bowl or cup. Add flour and mix into a paste. Return paste to sauce and stir.   Continue to boil slowly and stir until thickened, about 5 minutes or more.

*There are a lot of ways to roast garlic, but I often have pre-peeled cloves from Costco that I put on a cookie sheet with various dried herbs (oregano, thyme, sage, etc.) and pour some broth around them to keep them moist, then bake them for about an hour...can't remember the temperature, but probably around 350°?