In a medium pot, combine crushed tomatoes, stock concentrate, 2 cups water, 1 tsp sugar, ½ tsp salt, and pepper (3 cups water, 2 tsp sugar, and 1 tsp salt for 4 servings). Bring to a simmer over medium heat. Once simmering, cook, stirring occasionally, until reduced and slightly thickened, 5-8 minutes.

While soup simmers, wash and dry produce.

Slice tomato into ¼-inch-thick rounds; season with salt and pepper. Slice mozzarella into ¼-inch-thick rounds.

Once soup has simmered 5-8 minutes, using an immersion blender, blend directly in the pot until thickened and creamy, 60-90 seconds. TIP: Don’t have an immersion blender? Turn off heat; carefully transfer soup to a blender or food processor. Pulse until smooth, then cook through the rest of this step as instructed.

Stir in crème fraîche and blend again. Taste and season with salt and pepper. TIP: Prefer your soup chunky? Skip the blending!

In a small bowl, combine mayonnaise and half the basil paste (reserve the rest for serving).

Arrange baguette halves, cut sides up, on a clean work surface. Spread with basil mayo. Top with as much dressed arugula as you like. Layer evenly with sliced tomato and mozzarella. Close sandwiches.

Divide soup between bowls; drizzle with remaining basil paste.

Divide sandwiches between plates. Serve with any remaining dressed arugula on the side.