Green Bean Bake, revisited

my sister gave me this, modified from BH&G Nov. 2005

1 large sweet onion, cut into 1 inch wedges (can use white, yellow or red)
1/4 c cooking oil
3 Tbsp packed brown sugar
2 lb fresh or frozen whole green beans, trimmed
6 oz baby portobello or button mushrooms, halved
2 Tbsp olive oil
1 Tbsp soy sauce
2 Tbsp balsamic vinegar
6 oz softened cream cheese or goat cheese
2 to 3 Tbsp milk

In a large skillet cook onions, covered, in hot oil over medium-low heat for 13 to 15 minutes or until onions are tender. Uncover; add brown sugar.  Cook and stir over medium-high heat for 3 to 5 minutes or until onions are golden and caramelized.  Set aside.
Preheat oven to 400 degrees.
In a large saucepan cook green beans, covered, in a small amount of boiling water for 3 minutes.  Drain.
In a 3-qt baking dish combine green beans and mushrooms.  Combine olive oil, soy sauce, and balsamic vinegar.   Pour over vegetables, tossing to coat.  Roast for 15 to 20 minutes, stirring once, until crisp tender.
Meanwhile, in a medium mixing bowl beat together cheese and milk with an electric mixer on medium speed. Spoon cheese in lengthwise mounds along center of baking dish.  Top  with caramelized onions.
Return to oven; heat 5 to 8 minutes or until cheese and onions are heated thru.
Makes 10 to 12 servings.

To make ahead, prepare onions as directed.  Refrigerate until ready to assemble.  Prepared vegetables and mushrooms as directed; refrigerate until ready to assemble.  Remove onions and vegs from refrigerator 30 minutes before using.
To reheat, assemble dish as directed, omitting cheese mixture.  Heat in a 400 degree oven for 30 minutes.  The last 5 minutes of baking time, spook cheese mixture over onions.