Wash potatoes and place in a large pot. Cover with water and bring to a boil. Lower the heat and simmer for about 15 minutes. Drain and rinse with cold water to cool enough to handle. Cut larger potatoes in half, if necessary.
Preheat oven to 375 degrees Fahrenheit.
Add butter, minced garlic, and flour to a large saucepan. Sauté over medium heat until the mixture turns a light, golden color, about 6 to 7 minutes.
Add the milk and cream to the butter mixture, 1 cup at a time, whisking continuously until very smooth. Add onions, cheese, and meat. Season with white pepper and salt to taste.
Place potatoes in a casserole dish and top with sauce. Bake for 30 minutes or until golden brown in color.
Make sure to select your potatoes properly, avoid those with a greenish tinge as they may have been exposed to too much light and produced ‘solanine,’ a toxin that can cause headaches and stomach cramps.
Keep your potatoes uniform in size. Cut the bigger pieces into halves, so they cook evenly.
Keep from over-cooking your potatoes by checking for doneness near the end of the cooking time suggestion. Use a paring knife or fork and poke it. If it goes through smoothly, then your potatoes are ready!
Make sure to use a large enough casserole dish (best to fill it a third of the way). Filling it all the way to the top will cause the sauce to overflow, while filling it too low can cause over-cooking.
Make sure that you taste test your smoked meat before seasoning the sauce with salt. Smoked meats are generally salty, so adding too much salt on top of this will ruin the balance of flavors. You can rinse it with warm water if too salty before adding it to the sauce.
You can replace the green onions with leek. Use all the white parts and tender green parts.
Please keep in mind that nutritional information is a rough estimate and can vary significantly based on the products used and serving size.