thanks DS - my burgers were pretty darn tasty for sure. I forgot to mention in my post I sautéed my baby Portobello mushrooms - here's the method I used:
1 container of baby Portobello mushrooms (wiped clean and sliced)
1/4 cup red onions (diced small)
2 tablespoons butter
pinch of veggie seasoning (you can use a pinch of kosher salt)
ground black pepper
big splash of Sweet Marsala wine (I use Florio brand)
Cook mushrooms over medium heat until they start to softened and the Marsala wine is reduced down. Remove from the heat, cover pot with a lid and set aside until you are ready to add to the burgers.