Slice the Italian sausage into 1/2-inch rounds and brown them in a large skillet over medium-high heat for 5-7 minutes, stirring occasionally, until the exterior is golden and cooked through. While the sausage cooks, cut the cream cheese into 1-inch cubes—this helps it melt evenly into the soup without clumping. Roughly chop the spinach into 1-inch strips for easier eating once it's in the soup.

Transfer the cooked sausage to your slow cooker along with the broth, diced tomatoes (with their juice), cream cheese cubes, and garlic powder. Stir everything together thoroughly, breaking up the cream cheese slightly as you mix—this helps it distribute more evenly during cooking. I like to add the cream cheese in cubes rather than whole because it melts more smoothly and prevents lumps in the final soup.

Cover the slow cooker and cook on LOW for 4 hours. This gentle, extended cooking allows the flavors to meld together beautifully and gives the cream cheese plenty of time to dissolve fully into a rich, creamy broth. Stir occasionally if you're nearby, but it's not essential.

After 4 hours, add the tortellini and chopped spinach directly to the slow cooker and stir gently to distribute them evenly. Cover and cook on LOW for an additional 30 minutes, which gives the tortellini time to cook through and the spinach to soften and wilt into the soup. I find that adding these near the end keeps the tortellini tender rather than overdone, and the spinach retains better color and texture.

Ladle the soup into bowls and serve hot. The cream cheese will have created a rich, velvety broth, and all the components should be tender and fully cooked.