In a stock pot, add potatoes and salt, then fill with water until potatoes are covered 1 inch. Boil for 10-15 minutes or until fork tender. Drain, add 1 teaspoon of butter and the sour cream, then mash gently to blend together. Set aside.

In a cookpot or Dutch oven, brown the ground beef over medium-high heat, breaking into crumbles as it cooks. Remove meat and set aside, then drain off excess grease and return cookpot to the stove.

Melt remaining butter in the pot, then add onions and cook about 5 minutes or until softened. Add garlic and cook one additional minute. Whisk in flour and cook for one minute, stirring constantly. Slowly add the chicken broth, again stirring constantly to blend together. Scrape up any brown bits off the bottom while stirring.

Add Worcestershire sauce, Italian seasoning, dry mustard, and sage. Slowly add the half and half and combine thoroughly. Bring to a boil, then reduce heat to simmer.

Stir the potatoes into the broth mixture until well combined. If possible, use an immersion blender to make the mixture creamy, or use a standard blender in batches.

Add the ground beef and frozen vegetables into the cookpot and stir to combine. Heat through for about 5 minutes.

Remove cookpot from heat. Slowly add cheese and stir until melted and blended together. Check taste and add salt and pepper as desired.