In large skillet saute bacon until crisp drain on paper towel crumble and set aside
Pour bacon drippings from skillet
In the same skillet melt butter Use about 4 tablespoons of melted butter to brush the outsides of the mushroom caps and place in large shallow 13 x 9 x 2-inch baking pan
To the butter remaining add onion and saute then add mushroom stems and saute 2 minutes longer
Remove from the heat In bowl combine eggs cream cheese and salt