Why This Recipe Works

Double roast: Roasting the veg first concentrates sugars for caramelized depth before the cream bath.
Turnip advantage: Slightly peppery turnips lighten the richness and add intrigue next to creamy Yukon Golds.
Garlic-thyme oil: Infusing the cream with gently smashed cloves and fresh thyme gives layered aroma in every bite.
Crispy cheese lid: A final broil creates those irresistible frico edges everyone fights over.
Make-ahead magic: Assemble in the morning, refrigerate, then slide into the oven when guests arrive—perfect for holidays.
One pan, no fuss: Everything happens in the same baking dish—less washing up, more clinking glasses.

Ingredients You'll Need

I reach for small-to-medium turnips so their skins are tender enough to leave on—peeling feels like extra homework. Look for firm, unblemished specimens with bright purple-white skin. If they arrive with greens attached, save those for a quick sauté tomorrow morning.

Yukon Gold potatoes are my gold standard for gratins; they hold their shape yet soften into velvety slices. Avoid russets here—they'll dissolve into the cream and you'll miss the layered texture.

Heavy cream is non-negotiable. Lower-fat liquids break and water-log the dish. If you must, half-and-half works only if you add a tablespoon of flour to the pot while infusing.

Fresh thyme's lemon-pine perfume perfumes the cream; dried thyme tastes dusty in comparison. Buy a living pot from the produce section and you'll have sprigs all winter.

Garlic gets bashed once to open its shoulders, then swims in the warming cream so its flavor softens rather than shouts. If you're a garlic lover, add one extra clove—no more or it will eclipse the vegetables.

Gruyère melts like a dream and browns into nutty blisters. In a pinch, aged white cheddar or Comté work, but avoid pre-shredded cheese coated in anti-caking powder; it greases out.

A whisper of freshly grated nutmeg deepens the savory notes—buy whole nuts and grate once; the pre-ground jar lost its mojo months ago.

How to Make Warm Roasted Turnip & Potato Gratin with Garlic & Thyme

Heat the oven & prep the veg

Preheat to 425 °F (220 °C). Scrub potatoes and turnips; trim any hairy roots but keep the skin for rustic texture. Slice into ⅛-inch rounds using a mandoline or sharp knife—think thick potato-chip vibes. Toss in a large bowl with 2 Tbsp olive oil, 1 tsp kosher salt, and a few grinds of pepper until every slice is glossy.

First roast for caramel

Arrange slices upright in a 9×13-inch (or similar) baking dish, alternating potato-turnip-potato for color. Slide onto the middle rack and roast 25 minutes—edges should toast to light amber. This step evaporates surface moisture so the finished gratin isn't watery.

Infuse the cream

While veg roast, pour 2 cups heavy cream into a small saucepan. Add 3 gently smashed garlic cloves, 6 fresh thyme sprigs, ½ tsp kosher salt, and a few scrapes of nutmeg. Warm over medium-low until tiny bubbles appear at the rim—do not boil—then remove from heat, cover, and steep 10 minutes. Strain; discard solids.

Add cream & cheese

Reduce oven to 375 °F (190 °C). Slowly pour scented cream over the vegetables until it comes halfway up the sides—reserve 3 Tbsp for finishing. Scatter 1 cup grated Gruyère between the layers and another ½ cup across the top. Cover loosely with foil, tenting so it doesn't stick to the cheese.

Bake low & slow

Return to oven and bake 35 minutes. Potatoes should yield easily when pierced with a knife, and cream will have thickened into a silky sauce. If still soupy, bake 5–10 more minutes, checking every 5.

Uncover & broil to gold

Remove foil, drizzle reserved cream across the surface, and sprinkle remaining ½ cup cheese. Switch oven to broil. Broil 2–4 minutes, rotating once, until the top is blistered and the edges frico-crisp. Rest 10 minutes to set; garnish with fresh thyme leaves.

Expert Tips

Mandoline safety

Use the hand-guard or cut-resistant gloves—those blades are sharper than your chef's knife.

Even sizing

Pick potatoes and turnips of similar diameter so the slices nestle neatly.

Flavored cream

Swap thyme for rosemary or sage, or add a strip of lemon zest for brightness.

Crisp-top rescue

If baking ahead, reheat at 325 °F for 20 min, then broil just before serving.

Dairy-free?

Substitute full-fat coconut milk and vegan cheese; add 1 tsp white miso for umami.

Holiday timing

Roast veg and infuse cream up to 24 h ahead; assemble and bake while the turkey rests.

Variations to Try

Storage Tips

Cool leftovers completely, then cover tightly and refrigerate up to 4 days. Reheat single portions in a 325 °F oven for 15 minutes or microwave for 1–2 minutes, though the microwave sacrifices the crispy lid.

To freeze, bake the gratin without the final cheese topping. Cool, wrap in foil, then plastic, and freeze up to 2 months. Thaw overnight in the fridge, add fresh cheese, and bake at 350 °F until bubbly.

For meal-prep, roast the vegetables and infuse the cream on Sunday. Store separately, then assemble and bake mid-week in under an hour.

warm roasted turnip and potato gratin with garlic and thyme

Warm Roasted Turnip & Potato Gratin with Garlic & Thyme

Why This Recipe Works

Ingredients You'll Need