Cut the pumpkin bread into 1/2 to 3/4 inch cubes. Dry the cubes overnight or, lightly toast them in a slow oven for one hour in a single layer on a cookie sheet. Place bread cubes into large bowl, set aside.
Butter a 2 quart casserole dish and set aside.
Melt butter in large skillet. Add onion and sauté until slot and translucent, about 8 minutes. Add mushrooms and sauté for about 6 minutes.
Add the contents of the skillet into the bread cubes, toss lightly. Add stock and herbs, toss lightly until everything is well distributed. If mixture is too dry, add 2 additional tablespoons chicken stock.
Bake uncovered at 350 degrees F. for 40 minutes. Serve immediately.