1-First, shred the cheese from a block and let the sour cream and half and half reach room temperature for better texture. Cook and crumble 1 lb of ground beef over medium-high heat until fully cooked, then drain excess grease and set aside.

2-Next, peel and cut 4 large russet potatoes into thirds; boil them in water with 3/4 teaspoon salt until fork-tender, then drain and mash with 3/4 cup sour cream and 1 tablespoon salted butter, and set aside.

3-In a separate pot, melt the remaining 2 tablespoons salted butter, cook the diced yellow onion until softened, add 3 cloves minced garlic and cook for 1 minute more.

4-Whisk in 1/4 cup flour and cook for 1 minute. Gradually add 4 cups chicken broth, stirring to loosen any browned bits.

5-Incorporate 3/4 teaspoon Worcestershire sauce, 2 teaspoons Italian seasoning, 1/2 teaspoon mustard powder, and 1/4 teaspoon ground sage, then slowly add 2 cups half and half. Bring the mixture to a boil, then reduce to a simmer.

6-Stir in the mashed potatoes and blend until creamy using an immersion blender or regular blender. Add the cooked ground beef and 1 1/2 cups mixed frozen vegetables, and heat through for about 5 minutes.

7-Remove from heat, then gradually stir in 2 cups shredded cheddar cheese, ensuring the soup base is not too hot to maintain a smooth texture. Season with salt and pepper to taste before serving. The total prep time is about 15 minutes, with cook time around 45 minutes, making for roughly 1 hour overall.