Rachael's Provolone-Stuffed Meatballs With Kale

For the meatballs:

• 1/2 cup dry breadcrumbs, or panko breadcrumbs
• 1/3 cup whole milk
• 1 pound ground beef (80% lean)
• Salt and pepper
• 2 large cloves garlic, grated or finely chopped
• 1 teaspoon fennel seeds, or ⅓ palmful
• 1 cup (packed) baby kale or stemmed Tuscan kale, blitzed in a food processor until finely chopped
• 1 cup (loosely packed) grated Pecorino Romano, about 2 ounces
• 1 egg, lightly beaten
• 2 to 3 ounces provolone, cut into ½-inch cubes
• Olive oil cooking spray, or olive oil for brushing

For the sauce:

• 2 tablespoons olive oil
• 1 scant tablespoon Calabrian chile paste, or 1 teaspoon crushed red pepper
• 2 large cloves garlic, grated or finely chopped
• 2 tablespoons sun-dried tomato paste
• 1/2 cup sweet (red) vermouth, or red wine
• 1 teaspoon dried oregano
• One 14-ounce can crushed tomatoes
• 1 cup passata (uncooked tomato puree), or 1 cup tomato sauce
• 1/2 cup beef stock
• A few leaves of fresh basil, torn

Preheat the oven to 425˚F. Line a baking sheet with parchment paper.

In a medium bowl, mix the breadcrumbs and milk. Let stand until the crumbs soften, 3 to 5 minutes. Add the beef. Season with salt and pepper. Add the garlic and fennel seeds. Mix in the kale, Pecorino, and egg. Roll into balls about the size of a large walnut. Press 1 piece of provolone into each meatball, then enclose the cheese with the meat. Arrange on the baking sheet; spray with cooking spray or brush with oil. Roast the meatballs, turning once, until golden and cooked through, about 18 minutes.

Meanwhile, for the sauce, in a large skillet, heat the oil, two turns of the pan, over medium. Add the chili paste and garlic, and stir until aromatic, a minute or two. Stir in the tomato paste, then the vermouth and oregano. Stir in the tomatoes, passata, stock, and basil. Season with salt. Simmer the sauce over low heat while the meatballs finish cooking.

Add the meatballs to the sauce and turn to coat.