Preheat your oven to 400F and your smoker to 275F. Pick a wood you like - pecan, apple, hickory, or alder would work great.
Get a pot of water boiling with a tablespoon of salt.
Pop your onions in the zip-top bag, pour in the beaten eggs, and give it a toss. Mix the flour, panko, and a teaspoon of salt in a bowl and pour it into a shallow pan. Take the egg-coated onions and coat them with the flour mix.
Lay some aluminum foil on a baking sheet and spray it with nonstick spray. Spread the onions on the foil, don't overlap too much. Bake them in the oven, give them a stir every 5 minutes, for 20 minutes total. When they're golden brown, take them out to cool.
To blanch the green beans, pop them into the boiling water for 5 minutes, then drain and dunk them in cold water.
Now, let's sauté the mushrooms. Melt the butter in your skillet over medium-high heat. Toss in the mushrooms, a teaspoon of salt, and the pepper. Stir until the mushrooms soften, about 4-5 minutes. Add the garlic and stir for another minute.
Sprinkle the flour into the pan and stir to get rid of clumps. Cook for 2 minutes, then pour in the chicken broth. Stir vigorously, then add the half-and-half and let it boil. Turn down the heat and let it cook until it's thick and creamy, about 5 minutes. Turn off the heat and mix in the green beans.
Sprinkle the crunchy onions on top of the green bean mix and carefully transfer the skillet to your smoker. Close the lid and let it smoke for 30 minutes.
Take out the green bean casserole and serve it hot. Enjoy!