Mary Berry Vegetable Gratin

This one’s become my go-to when I need a crowd-pleaser that feels indulgent but still sneaks in a load of veg. The first time I made it, I was honestly just trying to use up a lonely squash and half a cabbage that had been in the fridge a bit too long. I didn’t expect much. But then I poured over that creamy cheese sauce, tucked it into the oven, and it came out bubbling and golden on top—pure comfort.

My first mistake? Rushing the roux. I ended up with a lumpy sauce and stringy bits of unmelted cheese. Once I slowed down and whisked properly, everything smoothed out. Now it’s silky, rich, and gets that just-browned top everyone fights over.

Let me walk you through how I got it just right.

What Makes This Recipe Special

Most vegetable gratins use boiled veg, but roasting the squash first brings out its sweet, nutty depth and keeps it from turning to mush. That alone lifts the whole dish.

Then there’s the cheese. Using a combo of Red Leicester and mature Cheddar gives you both colour and bite—it’s not just creamy, it has actual flavour. And a little Dijon mustard? Total game-changer. It doesn’t taste like mustard, but it gives the sauce a background tang that stops it from being bland.

You can prep it all ahead, too. I’ve assembled it the night before and baked it straight from the fridge. Works like a charm.

INGREDIENTS + WHY THEY MATTER

• Butternut squash (1 medium, about 750g) – Roasts beautifully, holds its shape. Adds a sweet base.
• Olive oil (2 tbsp) – Just enough to coat the squash and help it caramelise in the oven.
• Leeks (250g) – Adds a gentle onion flavour. Slicing thickly keeps them from going mushy.
• Savoy cabbage (200g) – Slightly earthy, and holds up better than spinach or softer greens.
• Butter and flour (60g each) – The base of your cheese sauce. Equal amounts keeps it smooth.
• Hot milk (600ml) – Warm milk blends better, no lumps. Cold milk just seizes the roux.
• Red Leicester (90g) – Adds richness and colour. Gruyère works too, but the orange looks lovely.
• Mature Cheddar (90g) – Punchy flavour. Mild just gets lost.
• Dijon mustard (1 tsp) – Trust me. Doesn’t taste like mustard, just lifts the sauce.
• Salt and pepper – Season everything in stages—don’t wait until the end.

Making It Yours (Without Ruining It)

• No cabbage? Kale or chard work. I’ve tried both—just blanch for a minute or so.
• Swap the cheese? Gruyère or Fontina instead of Red Leicester. I wouldn’t skip the Cheddar though—it anchors the flavour.
• Gluten-free? I’ve made the sauce with gluten-free plain flour and it worked well.
• Dairy-free? This one’s tricky. I tested a version with plant milk and vegan cheese—it was fine, but not quite as rich.

MISTAKES I’VE MADE (AND HOW TO AVOID THEM)

What Went Wrong	Why It Happens	How to Fix It
Sauce was lumpy	Cold milk added to hot roux	Warm your milk first and add gradually while whisking
Gratin was watery	Didn’t drain cabbage and leeks enough	Let them steam dry in the colander before mixing
Squash turned to mush	Over-roasted or cut too small	Cut into proper chunks (about 2.5cm), roast just until tender

HOW TO MAKE MARY BERRY’S VEGETABLE GRATIN

1. Preheat oven to 220°C (fan 200°C / 425°F).
2. Prepare squash: Peel, deseed, and chop into chunks. Toss with olive oil, salt, and pepper. Roast in a 1.7–2 litre baking dish for 20–25 minutes until just tender.
3. Boil the greens: Bring salted water to a boil. Simmer leeks for 3 minutes, add cabbage for 1 more. Drain well and let steam dry.
4. Make the sauce: Melt butter over medium heat. Whisk in flour and cook 1–2 minutes until golden. Off the heat, add hot milk slowly while whisking. Return to heat, whisk until thickened. Remove from heat again and stir in half the cheese and the mustard.
5. Assemble: Reduce oven to 200°C (fan 180°C / 400°F). Mix leeks and cabbage into the roasted squash. Pour cheese sauce over and stir gently.
6. Top and bake: Sprinkle with remaining cheese and a crack of black pepper. Bake 30–35 minutes until golden and bubbling.

TIPS FROM MY KITCHEN

• I always warm the milk in a jug in the microwave—cuts down on sauce lumps.
• Don’t skimp on seasoning the veg before adding the sauce—it really needs it.
• You can make the cheese sauce a day ahead—just keep it covered with clingfilm touching the surface to stop a skin forming.
• Let the whole gratin rest for 5 minutes before serving—it firms up nicely.

STORAGE + SERVING

• Fridge: Cool completely, store in an airtight container for up to 4 days.
• Freezer: Yes—freeze in portions for up to 3 months. Defrost in fridge overnight before reheating.
• Reheat: 180°C oven (fan 160°C) for 15–20 minutes until hot. Add a splash of milk if it looks dry.
• Serve with: A roast joint, sausages, or even just a green salad and crusty bread for a lighter meal.

FREQUENTLY ASKED QUESTIONS

Q: Can I make it ahead of time?
A: Absolutely. Assemble it fully, cover, and chill overnight. Bake from cold—just add 5–10 minutes to the cook time.

Q: What’s the best way to peel butternut squash?
A: Slice off both ends, cut it in half where the bulb meets the neck, then stand each piece up and shave the peel downwards with a sharp knife.

Q: Can I use frozen veg?
A: I wouldn’t recommend it here. They tend to release too much water and the gratin turns soggy.

Q: Can I use just one cheese?
A: Yes, I’ve used all Cheddar before—it’s still good, just a little less colourful.

Try More Recipes:

• Mary Berry Leek and Potato Gratin
• Mary Berry Porcini, Wild Mushroom, and Watercress Gratin Recipe
• Mary Berry Garlic Mushroom Penne Gratin