Trying to lighten up your green bean casserole? Try this quick and easy salad version, which combines fried shallots, croutons, mushrooms, green beans, and chopped chard leaves for a lighter take on a holiday classic.
Heat 2 tablespoons oil in a large skillet over medium-high heat until very hot but not smoking. Add half the shallots and cook, stirring, until golden brown and crisp, 3 to 4 minutes. Transfer with a slotted spoon to a paper-towel-lined plate. Repeat with the remaining shallots. Set aside. Leave any remaining oil in the pan.
Add bread to the pan and cook over medium heat until toasted, 5 to 6 minutes. Transfer to a small bowl.
Add the remaining 1 tablespoon oil to the pan and heat over medium-high heat. Add mushrooms and cook until golden brown, about 6 minutes. Transfer to a small bowl.
Add green beans and water to the pan, cover, and cook over medium heat until tender, 5 to 6 minutes.
Meanwhile, whisk mustard, vinegar, garlic, thyme, salt, and pepper in a small bowl. Add the mixture to the beans and cook until fragrant, about 30 seconds. Remove from heat and stir in chard, the mushrooms, and the croutons. Top with the reserved shallots.
To make ahead: Blanch green beans; cover and refrigerate for up to 1 day. Skip Step 4; instead stir beans into the pan with the mushrooms in Step 3 to heat through.