• Preheat the oven to 350 degrees.
• Add the butter to a large skillet set over a medium-high heat. Let the butter melt and when it starts to turn brown on the edges, swirl the pan. Keep swirling the pan until the butter becomes a deep brown color and smells very nutty. Turn the heat down to low and add the shallots. Season with 1/2 teaspoon salt and sugar. Coat the shallots in the butter and cook low and slow, stirring frequently until they are soft and caramelized, it should take about 15 minutes.
• While the shallots caramelize, bring a large pot of water to a rolling boil. While the water comes to a boil, set a colander in the sink. When the water comes to a boil, season with a little bit of salt. Add the green beans and cook for 3 minutes. Drain and then transfer to the colander. Rinse the green beans under cold water to stop the cooking process. Let drain.
• Once the shallots are tender and sweet, add the mushrooms. Stir to coat in the butter and shallots. Turn the heat up to medium and cook until the mushrooms have released their liquid, about 6-7 minutes.
• Add the sherry to the mushrooms and shallots. Bring the mixture up to a boil (you may need to turn the heat up) and simmer until the sherry has reduced by half. Stir in the flour. Cook for 1 minute. Using a whisk, slowly stir the milk in to the mushroom and shallot mixture. Bring the mixture to a boil and reduce to a simmer, simmer until thickened, it should take about 4-5 minutes. Remove from the heat and stir in the cheese. Stir until melted.
• Add the green beans to the sauce. Toss to combine. Transfer to a 9x9 baking dish or double the recipe and bake in a 9x12 casserole dish. Top with fried shallots and bake until hot and bubbly, about 30 minutes.

Fried shallots

• In a medium skillet, heat about ½ inch of canola oil. Heat to 375 degrees.
• In a small bowl, whisk flour, salt and black pepper. Place milk in another small bowl. Working in batches coat the shallots first in the milk, then flour (shaking off excess) and then into the hot oil to fry. When the onions become golden brown, remove with a slotted spoon and drain on a paper towel.