Prep ingredients:
Shred the cheese and measure the sour cream and half-and-half. Let them sit at room temperature.

Cook the bacon:
Cut bacon into 1-inch pieces and cook in a large pot over low heat, rotating occasionally. Remove crispy bacon and set aside, leaving 2 tablespoons of drippings in the pot.

Cook the potatoes:
Peel and cube potatoes into 1-inch pieces. Place in a stock pot, cover with water, add salt, and boil gently for 20 minutes until fork-tender. Drain and gently mash.

Sauté aromatics:
In the pot with bacon drippings, cook diced onion until softened (about 5 minutes). Add garlic and butter, cooking 1 more minute.

Make the roux:
Whisk in flour and cook for 1 minute, stirring constantly to remove raw flour taste.

Add liquids:
Gradually add chicken broth, scraping up any bacon bits from the pot for extra flavor. Slowly stir in half-and-half. Bring to a boil, then reduce to a simmer.

Combine potatoes and cream:
Stir in mashed potatoes, sour cream, and pepper.

Blend (optional):
For a smoother soup, use an immersion blender or transfer in batches to a blender.

Add cheese:
Gradually sprinkle in cheddar cheese, stirring until melted and creamy. Avoid adding cheese to a boiling base—it melts best when the soup is hot but not boiling.

Serve:
Garnish with crispy bacon and chives. Serve hot.