Preheat oven to 425 degrees. Wash and dry all produce. Trim, peel, and dice carrot into small pieces. Halve, peel, and finely chop onion. Dice tomato.
(JESSICA’S TIP: Skip this step—wet hands, form sausage into ½-inch balls, and set aside until step 4.) Heat a drizzle of olive oil in a large pot over medium-high heat. Add sausage and cook, breaking up meat into pieces, until browned and cooked through, 5-7 minutes.
Add another drizzle of olive oil to pot; stir in carrot, onion, and a big pinch of salt. Cook, stirring occasionally, until just softened, 5-7 minutes.
Add tomato, ¼ tsp garlic powder (½ tsp for 4 servings), and half the Italian Seasoning (use the rest of the spice as you like) to pot. Cook, stirring, until fragrant, 30 seconds to 1 minute. Stir in stock concentrates and 3½ cups warm water (6 cups for 4), scraping up any browned bits from bottom of pot. Add half the gemelli (all for 4). (JESSICA’S TIP: Stir in sausage meatballs now.) Cover, bring to a boil, then immediately reduce heat to low. Simmer until pasta is al dente (and meatballs are cooked through), 10 minutes.
Meanwhile, place 2 TBSP butter (3 TBSP for 4 servings) in a small microwave-safe bowl; microwave until just softened, about 10 seconds. Stir in 1 TBSP Parmesan (2 TBSP for 4), ¼ tsp garlic powder (use remaining garlic powder for 4), a pinch of salt, and a pinch of chili flakes. Halve ciabatta and spread with garlic butter; place cut sides up on a baking sheet. Toast in oven until golden and crispy, 4-5 minutes, then halve on a diagonal.
Stir spinach and 2 TBSP Parmesan (¼ cup for 4 servings) into soup until spinach has wilted. Season with plenty of salt and pepper. Divide soup between bowls. Sprinkle with remaining Parmesan and a pinch of remaining chili flakes if you like. Serve with toasts on the side.
