Grilled Marsala Chicken Sandwich with carmalized onions

Ingredients:
1 Tbs butter
1/2 tsp brown sugar
1/3 cup red onion, sliced
6 dates, chopped
1/8 cup marsala wine
1/4 tsp salt
1/8 tsp black pepper

1/4 cup mayonnaise, plus extra for spreading (for grilling)
4 ozs Wisconsin mascarpone cheese, softened
1 cup chicken breast, cooked and chopped
1/4 cup pecans, chopped
1 cup spinach leaves, fresh
4 slices Wisconsin Sharp Cheddar
8 slices Potato Bread (each piece spread on one side with mayonnaise, for grilling)

1.  In small saucepan, on medium heat add butter, sugar, onions, dates, wine, salt and pepper.  Sautee until onions become soft.  Remove off burner to cool.
2.  In medium mixing bowl add mayonnaise, mascarpone.  Mix well.
3.  On cutting board chop cooked chicken breast.  Add to mayo/mascarpone.  Mix well.
4.  Add contents of sauce pan (sautéed onions) to chicken.  Mix well.
5.  On heated skillet place 4 slices of bread (on med/low heat), greased side down.  Divide chicken mixture in quarters and place on top of bread.  Place fresh spinach on top and then one slice of Wisconsin Cheddar.  Top each sandwich with remaining slice of bread, greased side up.
6.  Grill until toasted.  Flip and toasted other side.  Serve.