Crispy Parmesan Vegetable Tian with Gruyère Panko Crust Step-by-step instructions

Before you start

Preheat the oven to 400°F (200°C). If making the caramelized onion-garlic confit from scratch, prepare it ahead of time and keep it warm or at room temperature. Slice all vegetables using a mandoline or a sharp knife to a uniform 3mm thickness.

Have the Gruyère-panko mixture and thyme-infused olive oil ready. Choose a 9-inch round ceramic baking dish that is oven-safe and attractive enough for serving.

Instructions

Prep and Spiral

1. 1Spread the confit and slice vegetables
   Preheat the oven to 400°F (200°C). Spread the caramelized onion-garlic confit evenly over the bottom of a 9-inch round ceramic baking dish. Using a mandoline or a sharp knife, slice the Yukon Gold potato, green zucchini, yellow squash, and Roma tomatoes into very thin 3mm coins. Keep each vegetable separate.
   Look for The confit forms a thick, even layer; the vegetable coins are uniform and thin enough to see through slightly.
   Tip A mandoline ensures even 3mm slices; if using a knife, aim for paper-thin rounds.
2. 2Arrange the spiral
   Starting at the outer edge of the dish, arrange the vegetable slices in an alternating pattern: potato, zucchini, yellow squash, tomato. Overlap the slices slightly and work in a tight spiral toward the center. Continue until the entire surface is covered.
   Look for The spiral is tight and colorful, with each vegetable visible in a repeating pattern.
   Tip Keep the slices in small stacks as you work to maintain the pattern.

The onion confit forms a smooth, aromatic base. The vegetable slices are thin and uniform, and the spiral is tight and colorful, with each vegetable clearly visible. The dish looks almost too pretty to bake, but resist the urge to eat it raw.

Top and Bake

3. 3Top with Gruyère-panko and oil
   Sprinkle the Gruyère-panko mixture evenly over the vegetable spiral. Drizzle the thyme-infused olive oil over the top, making sure to reach the edges.
   Look for The topping covers the vegetables completely, with a light sheen of oil.
   Tip Use your fingers to distribute the panko mixture evenly, especially into the crevices.
4. 4Bake until golden and blistered
   Place the dish in the preheated oven and bake for 40 minutes, until the vegetable edges are caramelized and the Gruyère-panko topping is golden brown and blistered. Rotate the dish halfway through for even browning.
   Look for The crust is deep golden and crisp, with some darker spots from blistering; the vegetables are tender when pierced with a fork.
   Tip If the top browns too quickly, loosely cover with foil for the last 10 minutes.

The Gruyère-panko mixture covers the vegetables evenly, and the thyme oil glistens. As it bakes, the kitchen fills with the aroma of caramelizing onions and melting cheese.

The crust turns golden and blistered, with some darker spots where the cheese has bubbled.

Garnish and Serve

5. 5Garnish and serve
   Remove the tian from the oven and let it rest for 5 minutes. Sprinkle with fresh basil ribbons. Use a spatula to lift portions onto plates, making sure to include the crispy crust.
   Look for The basil adds a bright green contrast; the crust stays crunchy when lifted.
   Tip Letting it rest helps the layers set, making it easier to serve neat slices.

Fresh basil ribbons add a bright, herbaceous note. When you lift a portion with a spatula, the crust holds its shape and crunches softly. The vegetables are tender and have absorbed the onion confit’s sweetness, creating a perfect balance of textures and flavors.

Common mistakes

One common mistake is slicing vegetables too thick, which prevents them from cooking through in the allotted time. Another is overcrowding the spiral, which can cause the vegetables to steam rather than roast.

Avoid using too much oil, which can make the crust soggy. Also, don’t skip the caramelized onion confit—it adds essential flavor and moisture. Finally, let the tian rest before serving so the layers settle and the crust stays crisp.

How to tell it’s done

The tian is done when the vegetables are tender and easily pierced with a knife, and the top is deep golden brown with blistered spots. The edges of the vegetables should look caramelized and slightly charred in places.

The internal temperature of the dish should be at least 165°F (74°C) if you are checking with a thermometer, though the vegetables are fully cooked when they are soft and the crust is crisp.