1. Place a rack in uppermost part of oven (or about 4" from heating element) and preheat broiler.
2. Place baguette slices on a baking sheet, transfer to oven, and broil until lightly browned on one side, 1 to 2 minutes; flip slices so untoasted sides are facing up and set baking sheet aside.
3. Combine butter and oil in a large nonstick skillet over medium-high heat and cook, stirring occasionally, until butter stops foaming, about 1 minute. Add mushrooms and shallots, season with salt and pepper to taste, and cook, stirring frequently, until mushrooms have released their liquid and begun to brown, 8 to 10 minutes.
4. Add Worcestershire sauce and cook, stirring constantly, until liquid is mostly evaporated, about 1 minute; remove skillet from heat and set aside.
5. Place two pieces of cheese on each piece of toast, then return baking sheet to oven and broil until cheese just begins to melt, 2 to 3 minutes. Divide mushrooms evenly over tops of toasts, then sprinkle with tarragon and serve.
Source: Hannaford fresh Magazine, December 2019