Heat oven to 400°F. Grease large 11x16 baking dish (with fruit/flower bottom) with cooking spray, and set it aside.

Sautee onions/garlic: Melt a little butter in a large saucier pan over medium heat. Add onion, and sauté for 4-5 minutes until soft and slightly browned. Add garlic and sauté for an additional 1-2 minutes until fragrant. Remove to a plate.

Make roux: To the same pan, melt remaining flour or fat. Whisk in flour until smooth, and cook for 1 more minute.Gradually pour in the stock, and whisk until smooth. Add in the milk, salt, pepper, thyme and reserved onions/garlic. Whisk until combined. Continue cooking for an additional 1-2 minutes until the sauce just barely begins to simmer around the edges of the pan and thickens. (Avoid letting it reach a boil.) Then remove from heat and set aside.

Meanwhile, slice potatoes using the 2mm thick disk. Rinse. Spread 1/3 of the sliced potatoes in an even layer on the bottom of the pan. Top evenly with 1/3 of the cream sauce, 1 cup of the shredded cheddar cheese then green onions. Repeat with another 1/3. Finish with the remaining 1/3.

Bake: Cover the pan with aluminum foil and bake for 30 minutes. The sauce should be nice and bubbly around the edges. Then remove the foil and bake uncovered for 25-30 minutes, or until the potatoes are cooked through and browned.

Note: Made 7/29/18 for Jeff, Em, John, Chrissy, kids. 4mm blade too thick. Next time 2mm. Bacon didnt add much so next time eliminate. Made for 2021 Xmas party. 2mm blade perfect. Not enough cheese. Intentionally left out salt cuz of cheese and bacon, but it did need a little. Made for family party 12/16/23. A bit dry so I upd the milk above. Added more cheese. Best to grate the cheese yourself just before adding. For Xmas party 2024 (20 people): Used larger dish and scaled up to 18 and used red and while baking dish. Still not enough cheese and too much cream sauce. But no changes above yet.