Wipe the mushrooms clean and carefully remove the stems; discard the stems or save for another use. Arrange the caps, cut side up, on a parchment-lined baking sheet.
Melt the Earth Balance in a small skillet. Add the remaining ingredients and stir until blended together. Remove from the heat.
Stuff the mushroom caps with the mixture from the skillet, distributing evenly. Cover the baking sheet loosely with foil. Bake, covered, for 10 minutes, then uncover and bake for 10 minutes longer, or until the mushrooms and filling are beginning to brown.
Transfer to a platter and garnish with thyme. Serve warm.