Preheat the oven to 425°F. Add carrots, 2 tsp vegetable oil, and a pinch of salt and pepper to a baking sheet, and toss. Roast until carrots are tender and golden brown, 20 to 25 minutes. (4-serving meal: use 4 tsp vegetable oil)

Heat 1 tbsp vegetable oil in a large nonstick skillet over medium-high heat. Add mushrooms and cook, undisturbed, until they start to brown, 2 to 3 minutes. Add garlic and cook until fragrant, 1 to 2 minutes. (4-serving meal: use 2 tbsp vegetable oil) TIPS: You will use this skillet in a later step. Remember to wipe mushrooms clean with a damp kitchen towel.

Add 2 tbsp mayo to a small bowl and set aside. In a separate small bowl, combine remaining mayo, Dijon mustard, horseradish, and a pinch of salt and pepper and stir the horseradish mayo. (4-serving meal: use 4 tbsp mayo)

Add caraway seeds to the reserved mayo and stir the caraway mayo. Spread caraway mayo on the sourdough bread. Flip bread over and spread 2 tsp horseradish mayo on each slice. Add cheese, mushrooms, and sauerkraut to 2 bread slices, and close sandwiches with the remaining slices (with the caraway mayo facing up).

Wipe the large nonstick skillet clean and return it to medium-high heat with 1 tbsp vegetable oil. Add mushroom reubens to the skillet and cook until the cheese is melted and bread is golden brown, 5 to 6 minutes per side. (4-serving meal: use 2 tbsp vegetable oil) TIP: You can use a spatula to press gently on the sandwiches as they cook.

Slice the mushroom reubens in half and place on plates. Add carrot fries and a dollop of horseradish mayo. Tuck in!