Wash and dry all produce. Preheat broiler to high or oven to 500 degrees. Trim, then thinly slice mushrooms. Halve, peel, and thinly slice half the onion (use the other half as you like). Strip thyme leaves from stems; discard stems.

Heat a drizzle of olive oil in a large pan over medium heat (use an ovenproof pan if you have one). Add mushrooms, onion, and thyme. Cook, tossing, until softened, 5-6 minutes. Season with salt and pepper. Stir in stock concentrate and 11/2 cups water. Bring to a simmer.

Add ravioli to pan, spreading them out in an even layer. Cover and cook for 4 minutes. Uncover and cook, spooning stock over ravioli occasionally, until tender, 5-6 minutes more. TIP: If liquid evaporates before ravioli are tender, add a splash of water to pan; shake pan to keep ravioli from sticking.

While ravioli cook, combine 1/4 cup panko (we sent more), Parmesan, a drizzle of olive oil, and a pinch of salt and pepper in a small bowl.

Add sour cream to pan and gently stir to coat ravioli and create a thick sauce. (TIP: If sauce seems dry, add a splash of water.) Season with salt and pepper. If your pan is not ovenproof, transfer mixture to a small baking dish at this point.

Sprinkle crust over ravioli. Transfer pan to broiler (or oven) and broil until crust is golden and crisp, 1-2 minutes. Divide ravioli between plates and serve.