Saute mushrooms in butter until tender.

Place about 3/4 of the cheese on toast and top with mushrooms.

Sprinkle last of the cheese over mushrooms.

Place in a toaster oven briefly to melt cheese.

In a 1-quart saucepan, fill halfway full with about 1/4 cup vinegar.

Bring to a boil then reduce to a simmer.

Crack eggs separately into small dishes.

Swirl water to get a whirlpool going, then slide in each egg.

Simmer eggs 4 minutes, then lift out with a slotted spoon.

Dab off water from bottom of eggs with a paper towel then slide onto the mushroom toast.

Season with salt, pepper and chives.