Potatoes Au Gratin with Caramelized Onion
Submitted By: Kelsie S.
Ingredients:
2 ½ Lbs Yukon Gold Potatoes - peeled or unpeeled (your choice)
1 Sweet Onion (ie: Vidalia, Walla Walla, Texas Super Sweet, or Sweet Imperial)
4 Tbs Unsalted Butter - divided
3 Tbs All Purpose Flour
2 Cups Half and Half - can substitute whole milk if desired
1 Cup Sharp Cheddar Cheese - grated
½ Cup Gruyère Cheese - grated
1 Tbs Olive Oil
Fresh Ground Black Pepper to taste
Kosher Salt to taste
-OPTIONAL-
1 tsp Mustard Powder
Preparation:
- Halve and thinly slice the onion
- Heat olive oil and one Tbs of the butter in a medium/large skillet over medium-high heat until shimmering - Add onion along with ½ tsp kosher salt and ¼ tsp fresh ground black pepper - Sauté (stirring occasionally) until medium brown and caramelized (apx 20 minutes) - remove from heat and set aside until needed
- Preheat oven to 400ºF
- Wash and slice your potatoes into thin disks (apx ⅛ inch thick)
- Grease a medium casserole or baking dish and then make alternating stacks of potato and onion and stand upright (on edge) completely filling the dish
- Melt the remaining 3 Tbs of butter in a small skillet over medium heat - Whisk in the flour a little at a time until fully combined - Allow to cook (stirring constantly) for 2-3 minutes to make a 'golden roux' - Whisk in the mustard powder (if using) and half and half - Continue to whisk over medium heat until 'thick and bubbly' (apx 4 minutes)
- Remove from heat and whisk in the grated cheeses a little at a time allowing each addition to fully melt before adding the next until all of the cheese has been incorporated - Adjust seasoning with salt and pepper to taste
- Pour the cheese sauce evenly over the top of the potatoes - Cover with aluminum foil - NOTE: You may want to grease the foil where it may make contact with the potatoes and sauce to ensure ease of removal
- Place in the top third of the oven and allow to bake for 60 minutes - After 60 minutes, remove foil and continue to bake until the top is lightly browned and the potatoes are cooked through and tender (apx 25 minutes more)
- Serve hot
