Creamy Turnip and Potato Gratin with Caramelized Onion Crust

Elevate your next dinner with this sophisticated yet simple potato and turnip gratin. By combining the earthy, starchy goodness of potatoes with the subtle sweetness of baby turnips, you create a side dish that is far more complex and interesting than standard scalloped potatoes.

The addition of caramelized onions provides a savory backbone that perfectly complements the rich, thyme-scented cream, all topped off with a crispy, blistered white cheddar crust that defines true culinary comfort.

This gratin is the ideal solution for those seeking a side dish that balances elegance with rustic charm. The process focuses on thin, uniform layering which allows the vegetables to absorb the thyme-infused cream, resulting in a velvety texture throughout the dish.

The two-stage baking process is crucial: first, covered to ensure the vegetables become fork-tender, and second, at a higher temperature to achieve that signature golden, bubbly crust. It is a reliable dish that pairs beautifully with roasted meats or stands alone as a hearty vegetarian centerpiece.

Ingredients

Why this recipe works

The method of slicing vegetables thinly on a mandoline ensures that they cook at the same rate, preventing mushy or undercooked sections. Layering the caramelized onions throughout the dish, rather than just on top, allows their sweetness to permeate every single bite, creating a balanced flavor profile that bridges the gap between the savory cheddar and the natural sugars of the turnips.

By using a two-temperature baking approach, the recipe achieves two distinct goals. The initial 375°F bake uses steam to soften the dense root vegetables, while the final 425°F blast caramelizes the cheese and reduces the cream into a rich, thick sauce. This technique prevents the cheese from burning before the potatoes and turnips have fully cooked, ensuring the final result is perfectly textured from edge to center.

Notes and substitutions

When selecting ingredients, choose firm Yukon Gold potatoes as they hold their shape well while maintaining a creamy interior. The choice of baby purple-top turnips is intentional for their mild, slightly sweet flavor; if you cannot find them, any small white turnip will work.

The thyme-infused cream should be prepared by gently warming the cream with fresh sprigs of thyme and allowing it to steep for at least 15 minutes before pouring it over the vegetables.

The choice of equipment is straightforward, but the mandoline is indispensable for achieving the required 2mm thickness. If you do not have a mandoline, you can use a sharp chef's knife, though you must take care to keep the slices as thin and uniform as possible.

Ensure your baking dish is well-buttered to prevent sticking, and use a high-quality aged white cheddar for the best melt and flavor depth in the final crust.

• Yukon Gold potatoes: Russet potatoes or any starchy potato variety
• Vermont white cheddar: Gruyere or sharp white cheddar from any region

Equipment

• Mandoline slicer
• 9x13 inch baking dish
• Aluminum foil
• Mixing bowl
• Chef's knife
• Cutting board