- 3 tablespoons extra-virgin olive oil
- 2 large or 4 small shallots, thinly sliced
- 3/4 teaspoon kosher salt, plus extra for seasoning
- 1/4 teaspoon freshly ground black pepper, plus extra for seasoning
- 2 cloves garlic, minced
- 1 1/2 pounds (about 2 medium) russet potatoes, peeled and cut into 3/4-inch pieces
- 3 cups low-sodium chicken broth
- 1 cup arugula
- 1/2 cup mascarpone, at room temperature
- 2 (1/2-inch thick) slices sourdough or multi-grain bread, cut into 1/2-inch cubes
- 2 tablespoons extra-virgin olive oil
- 1/4 teaspoon kosher salt
- 8 cherry or grape tomatoes, quartered
For the soup: In a large saucepan or Dutch oven, heat the oil over medium heat. Add the shallots and season with a pinch of salt and pepper. Cook, stirring frequently, until tender, about 3 minutes. Add the garlic and cook until aromatic, about 30 seconds. Add the potatoes, chicken broth, and arugula. Bring to a boil. Reduce the heat, cover, and simmer until the potatoes are very tender, about 15 minutes. In batches, ladle the mixture into a blender or food processor and blend until smooth. Return the soup to the saucepan and whisk in the cheese, 3/4 teaspoon salt, and 1/4 teaspoon pepper. Let the soup cool to room temperature, about 30 minutes. Refrigerate for at least 1 hour until ready to serve. Before serving, adjust the seasoning with salt and pepper, to taste.
For the croutons: Place an oven rack in the center of the oven. Preheat the oven to 375 degrees F.
In a small bowl, toss together the bread, oil, and salt until coated. Spread in a single layer on a small baking sheet. Bake until golden, 10 to 12 minutes. Cool for 10 minutes.
To serve: Ladle the soup into small bowls. Garnish with croutons and cherry tomatoes.