Brown the Italian sausage and chopped onion in a medium skillet over medium-high heat for about 4-5 minutes until browned and translucent.

Add minced garlic to the skillet and cook for an additional minute until fragrant.

Transfer the browned sausage mixture to the slow cooker.

Add chopped potatoes, chicken broth, salt, pepper, and red pepper flakes to the slow cooker. Stir well to combine.

Cover the slow cooker and set it to low for 4-5 hours or high for about 2 hours.

When the potatoes are tender, stir in the chopped kale and heavy cream, and let it cook for an additional 30 minutes on low.

Before serving, taste and adjust the seasonings with additional salt, pepper, or red pepper flakes as desired.