Prep ingredients: Peel and finely chop 11⁄2 cups onion. Peel and finely chop 2 teaspoons garlic. Coarsely chop broccoli. Coarsely grate cheddar on the large holes of a box grater.

Sauté vegetables: In a medium pot, heat 1 tablespoon oil over medium-high until shimmering. Add onions, broccoli, 11⁄2 teaspoons of the garlic, and 1 teaspoon salt. Cover and cook, stirring occasionally, until broccoli is crisp-tender, about 5 minutes.

Add broth: When broccoli is crisp-tender, stir in broth concentrate and 2 1⁄2 cups water. Cover and bring to a boil. Uncover and cook over medium until liquid reduces slightly and broccoli is very tender, about 4 minutes. Add peas and cook, about 1 minute more. Remove from heat.

Add cheeses & blend soup: Off heat, add mascarpone and half of the grated cheddar in large pinches, stirring until melted before adding more. Using an immersion blender or regular blender, purée the soup until smooth. Season to taste with salt and pepper. Cover to keep warm until ready to serve.

Prep ciabatta: Preheat broiler with a rack in the upper third. Split ciabatta rolls. Brush generously on both sides with oil. Place on a rimmed baking sheet, cut side-down. In a small bowl, combine remaining cheese and garlic with a pinch each salt and pepper.

Broil ciabatta & serve: Broil ciabatta until lightly browned on first side, 1–2 minutes (watch closely as ovens vary). Flip and top with cheese- garlic mixture. Broil until cheese is melted and bubbling, 1–2 minutes more (watch closely). Halve each slice diagonally. Serve soup garnished with a drizzle of olive oil and a few grinds pepper with ciabatta alongside.