Remove stems from mushrooms. Slice mushroom caps thinly.
Over medium-high heat, melt butter. Cook mushroom caps and lemon juice until tender.
Remove mushrooms using a slotted spoon. Add onion and mushroom stems. Reduce heat to medium-low and cook until onion is tender.
Stir in the flour and cook until thickened.
Stir in the water and bouillon, making sure to dissolve all the flour.
Blend all the liquid, onions, and mushroom stems.
Over medium heat, bring the liquid to a boil, and heat until thickened.
Add the mushroom caps, whipping cream, salt, and pepper.
