Heat a large skillet over medium-high heat and cook ground beef for 6-8 minutes until completely browned. Drain excess fat, leaving about 1 tablespoon.
Add diced onion and minced garlic to the skillet with beef. Sauté for 3-4 minutes until onion is translucent and garlic is fragrant.
Stir in cream of mushroom soup, cheddar cheese soup, milk, salt, pepper, and paprika. Mix until well combined and smooth.
Layer half of the thinly sliced potatoes in the bottom of a 6-quart slow cooker, overlapping slightly and covering the entire bottom.
Spread half of the beef mixture evenly over the potato layer, reaching the edges.
Repeat layers with remaining potatoes and beef mixture. Press down gently to compact.
Cover and cook on low for 6-8 hours or on high for 3-4 hours until potatoes are fork-tender throughout, including the top layer.
About 15 minutes before serving, sprinkle shredded cheddar cheese over the top. Cover and let melt.
Garnish with sliced green onions before serving.
Notes
Use russet potatoes for best texture. Peel and slice them uniformly (about 1/4 inch thick) for even cooking.
A mandoline slicer helps create consistent potato slices.
Requires a 6-quart slow cooker.
Add diced jalapeños or cayenne pepper for a spicy kick.
Freezes well for up to 3 months. Thaw overnight before reheating, or reheat from frozen at 350°F for 45-50 minutes.
Cool to room temperature within 2 hours before refrigerating for food safety.