Wash green beans and break off ends and discard.  Then break beans into smaller pieces if desired.  I break the beans into 3 to 2 pieces depending on how long they are.

Place beans into boiling water (with no salt in the water) for 3 minutes or slightly longer for a more tender bean.  Remove beans and blanch in a bowl of ice water for 5 minutes.  Remove from ice water and drain.

Layer the blanched string beans in the bottom of a greased casserole dish (I used an 11x 7 dish).

Melt butter in a large skillet. Sauté the mushrooms, onions and garlic in the butter until the onions are soft, add the can of mushroom soup. Stir to combine soup and vegetables in the skillet, pour mixture over the string beans.

Sprinkle with Panko Bread Crumbs. Bake at 350º for 20 minutes or bread crumbs are browned.