In a multi-cooker pot, use the "Brown" or "Saute" function to cook the ground beef until browned, about 5 minutes. If your slow cooker doesn't have a similar function, brown the meat in a skillet over medium-high heat.
Add the diced onion and cook until translucent, about 4 minutes. Add the garlic, Italian seasoning, oregano, basil, red pepper flakes, and salt. Cook until fragrant, about 1 minute.
If you used a skillet, transfer the seasoned meat to your slow cooker pot. Add the crushed tomatoes and vegetable broth. Stir to combine.
Cover and set to slow cook on “Low” for 4-5 hours.
Stir in the tortellini. Cook for 30 minutes, until the pasta is hot and cooked through. Just before serving, add the kale.
Notes
Storage: Store in an airtight container in the refrigerator for up to 3 days. If you're enjoying this soup the next day (and beyond), you can expect the tortellini to be a little soft and puffy as it absorbs the broth over time.Substitutions and variations:
Beef: Instead of ground beef, use 500g ground Italian sausage meat, or 4-6 Italian sausages with the casings removed. To make it spicy, use hot Italian sausage.
Italian seasoning: To make your own Italian seasoning, combine 2 tablespoons dried oregano + 2 tablespoons dried basil + 1 tablespoon dried thyme + 1 tablespoon dried rosemary + 1 tablespoon dried sage leaves. Makes a little less than ½ cup.
Broth: Use your favourite broth (or whatever you have on hand); beef, chicken, or mushroom broth will work here too.
Pasta: Use your favourite fresh ravioli instead of tortellini.
Cream: For a thick, creamy broth add 1 cup heavy cream and 1 cup grated parmesan when you add in the pasta.