Begin boiling water in a large soup pot or Dutch oven. Once a boil is reached, add the baking soda and bouillon.

Boil the green beans for 5 minutes.

Drain well and rinse with cold water to stop them from cooking further. Spread out on a clean dish towel to dry.

Preheat oven to 375° F.

Combine the chicken broth, half and half, Worcestershire sauce, onion powder, parsley, mustard powder, salt, and pepper in a medium measuring cup with a spout. Set aside.

Dice the mushrooms and cut the green beans in halves or thirds.

Use the same pot that you used to boil the green beans and melt 3 tablespoon butter over medium heat. Add the mushrooms, garlic, and a pinch of salt and cook for 4-5 minutes, stirring continuously.

Add the remaining butter and the flour and cook for 2 more minutes.

Add the chicken broth mixture in small splashes, stirring continuously.

Bring it to a boil, then reduce to a simmer. Let it bubble gently for 4-5 minutes, or until desired consistency is obtained. Stir occasionally as it cooks.

Remove from heat. It will thicken a little more upon standing.

Stir in the Parmesan cheese along with half of the cheddar cheese and half of the crispy fried onions. Add the green beans and stir to combine.

Transfer to a lightly greased baking dish. Top with remaining cheese and fried onions.

Bake uncovered for 20 minutes, or until the top is brown and bubbly. Serve!