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

Melt 1 TBSP butter in a large pan over medium heat (use an ovenproof pan if you have one). Add thyme and onion. Cook until softened, 5-6 minutes. Season with salt and pepper. Pour in stock concentrate and 1 cup water and bring to a simmer.

Once stock mixture is simmering, add ravioli to pan. Cover and cook 4 minutes. Uncover and increase heat to high. Continue cooking, spooning stock over ravioli, until ravioli are tender and stock has reduced, 5-6 minutes. Shake pan occasionally to keep ravioli from sticking.

Combine panko, Parmesan, a drizzle of olive oil, and a pinch of salt and pepper in a small bowl.

Remove pan from heat. Carefully stir sour cream and spinach into pan until thoroughly combined and spinach is wilted. Season with salt and pepper. (TIP: Add up to 1/2 cup water if sauce seems very thick.) If your pan is not ovenproof, transfer mixture to a baking dish at this point.

Sprinkle ravioli in pan (or dish) with crust mixture. Place under broiler and broil until golden brown, 1-2 minutes. Divide between plates and serve.