Preheat the broiler to high. Thinly slice the garlic. Remove and discard the kale stems and ribs, then thinly slice the leaves.

Heat a drizzle of olive oil in a medium oven-proof pan over medium heat. Add the garlic and cook, tossing, for about 1 minute, until fragrant. Add the kale and a splash of water and cook, tossing, for 3-4 minutes, until soft. Season with salt and pepper.

Add the milk, stock concentrate, 1/2 cup water, and 1/4 cup pesto to the pan and stir to combine. Add the tortellini to the pan. Don’t worry if they aren’t submerged! Bring the mixture to a boil, then reduce to a simmer and cook, stirring occasionally, for 5-7 minutes, until the sauce becomes very thick and the tortellini are soft. TIP: If you do not have an oven proof pan, transfer the tortellini to a small (8x8-inch) baking dish before the next step.

Make the panko topping: While the tortellini simmers, combine the panko, Parmesan, and 1/2 Tablespoon olive oil in a small bowl. Season the mixture with salt and pepper, then sprinkle the panko topping over the tortellini.

Transfer the pan to the oven to broil for 1-2 minutes, until browned and bubbly. Divide the tortellini gratin among bowls and dig in!