Wash and dry all produce. Halve and peel onion, then thinly slice. Mince a few slices until you have 1/4 cup minced onion and set aside. Heat a large drizzle of oil in a large pan over medium heat. Add sliced onion and cook, stirring, until soft and browned, 12-14 minutes. Stir in 1 tsp sugar and cook 1 minute more. Season with salt and pepper.

While onion cooks, pick basil leaves from stems; discard stems. Finely chop half the leaves. Remove and discard large ribs and stems from kale; cut or tear leaves into bite-size (roughly 1-inch) pieces. Thinly slice mozzarella.

Remove onion from pan and set aside. Carefully wipe out pan with a paper towel. Heat a drizzle of oil in same pan over medium heat. Add kale and cook, tossing, until wilted and tender, about 4 minutes. Remove from pan and set aside.

Spread 1/2 TBSP butter on one side of a slice of bread. Repeat with remaining bread. Place two slices buttered-side down on your surface. Top with mozzarella, kale, onion, and whole basil leaves. Top with remaining bread, buttered-side up. Place in pan used for kale over medium heat. Cook until toasted and melty, 4-5 minutes per side. TIP: Press down gently with a spatula to help sandwiches toast evenly.

Meanwhile, heat a drizzle of oil in a medium pot over medium-high heat. Add minced onion and cook, stirring, until softened, 3-4 minutes. Pour in marinara sauce, 11/2 cups water, and stock concentrate. Stir to combine. Bring to a boil, then lower heat and reduce to gentle a simmer. Season with salt and pepper.

Remove pot with soup from heat and stir in chopped basil. Divide soup between bowls and dollop with sour cream. Slice sandwiches in half and serve with soup. TIP: Dip the sandwiches into the soup as you’re eating to get the best of both worlds.