Dijon Scalloped Potatoes

Christmas Day at the O'Briens'. Different vibe. Louder. More people. More chaos. Patrick and Colleen's house in Greenfield is a split-level that was built for a family of four and routinely holds a family of twenty. Megan's brothers Kevin and Sean were there with their wives and kids. Kevin has two boys, both under five, who treated the living room like a demolition site. Sean has a baby girl who screamed through dinner with the commitment of someone training for a career in opera.

The food was different from Wigilia. This was an Irish-American Christmas: ham, roasted potatoes, Colleen's soda bread, green bean casserole, and a trifle that Colleen makes every year that is mostly just cake soaked in sherry and whipped cream. I brought pierogi because I will always bring pierogi and also because Patrick asked me to. He pulled me aside before dinner and said, "You brought those dumplings, right?" I said, "Of course." He said, "Good man." Patrick's approval comes in two-word sentences.

Kevin and Sean are exactly as intimidating as advertised. They're both cops. They're both bigger than me. They both shook my hand like they were testing whether I could take a hit. Kevin said, "So you're the beer guy." I said, "I'm the pierogi guy." He said, "Megan says you're the beer guy." I said, "I'm both." Sean just looked at me for a long time without saying anything. This is a tactic they teach at the police academy and it is effective.

But the pierogi won them over. Kevin ate six. Sean ate eight and then asked me how to make them. I offered to teach him. He said, "Maybe." From a cop who was trying to intimidate me an hour ago, "maybe" is basically "yes, please, and also I accept you into this family."

Drove home that night with Megan in the passenger seat, both of us full of ham and pierogi and trifle and the particular exhaustion of spending eight hours with two families in two days. She fell asleep against the window. I drove through the Christmas lights on Mitchell Street and felt like the luckiest guy in Milwaukee.

Somewhere between Kevin eating his sixth pierogi and Sean asking me — in his best intimidating-cop monotone — how to make them, I started thinking about what it actually takes to win over a table full of strangers. It’s not the main dish. It’s the thing on the side that everybody reaches for twice without thinking about it. Colleen’s roasted potatoes were gone before the ham was half-carved, which told me everything I needed to know. So for the next big dinner — whoever’s house it ends up at — I’m bringing these Dijon scalloped potatoes: rich, a little sharp, completely unfussy, and exactly the kind of dish that makes a cop put down his guard and ask for the recipe.

Prep Time: 20 min | Cook Time: 1 hr 10 min | Total Time: 1 hr 30 min | Servings: 8

Ingredients

3 lbs Yukon Gold potatoes, peeled and thinly sliced (about 1/8 inch)
3 tablespoons unsalted butter
1 medium yellow onion, thinly sliced
3 cloves garlic, minced
3 tablespoons all-purpose flour
2 cups whole milk
1 cup heavy cream
3 tablespoons Dijon mustard
1 teaspoon kosher salt, plus more to taste
1/2 teaspoon black pepper
1/4 teaspoon ground nutmeg
1 1/2 cups shredded Gruyere cheese, divided
1/2 cup shredded sharp cheddar cheese
2 tablespoons fresh thyme leaves (or 1 teaspoon dried)

Instructions

Preheat and prep. Preheat your oven to 375°F. Butter a 9x13-inch baking dish and set aside. Slice potatoes thin and uniform — a mandoline helps here, but a steady hand works too.
Build the base. Melt butter in a medium saucepan over medium heat. Add onion and cook until softened, about 5 minutes. Add garlic and cook 1 minute more, until fragrant.
Make the sauce. Whisk flour into the onion mixture and cook for 1 minute to eliminate the raw flour taste. Slowly pour in milk and cream, whisking constantly to prevent lumps. Bring to a gentle simmer and cook until the sauce thickens slightly, about 4–5 minutes.
Add mustard and seasoning. Remove from heat and whisk in Dijon mustard, salt, pepper, and nutmeg. Stir in 1 cup of the Gruyere until melted and smooth. Taste and adjust seasoning.
Layer the potatoes. Arrange half the sliced potatoes in an even layer in the prepared baking dish. Pour half the sauce over the potatoes. Scatter half the thyme. Repeat with remaining potatoes, sauce, and thyme.
Top and cover. Combine remaining 1/2 cup Gruyere and the cheddar; sprinkle evenly over the top. Cover the dish tightly with foil.
Bake covered. Bake covered for 45 minutes, until the potatoes are just beginning to soften when pierced with a knife.
Finish uncovered. Remove foil and bake an additional 25–30 minutes, until the top is golden and bubbling and the potatoes are completely tender. Let rest 10 minutes before serving — this helps the layers set so it slices cleanly.

Nutrition (per serving)

Dijon Scalloped Potatoes — The Side Dish That Belongs at Both Tables