Add the potatoes, vegetable broth, onions, & garlic to the slow cooker. Cover and cook on low for 4 to 6 hours or on high for 3 to 4 hours (until potatoes are fork tender). Using a potato masher, mash the potatoes in the slow cooker, leaving some potatoes chunky.

in a large saucepan over medium high heat, melt the butter. Add the flour and stir with a whisk until the mixture is golden & bubbly, about 1 to 2 minutes.. Add the sour cream, whole milk, & heavy cream. Stir with the whisk until the mixture is incorporated & smooth. Add 1 cup of the grated cheese. Stir with the whisk until melted & smooth

Slowly add the cheese mixture to the slow cooker. Add salt & pepper to taste. Stir and cook for 15 to 20 additional minutes.

Serve topped with the remaining grated cheese, green onions, etc.