Baked cheese and onion pasta

A mustardy cheese sauce turns pasta, onion and spinach into a golden bake.

This recipe makes 4 servings and takes about 15 minutes to prepare plus 30 minutes to cook. Metric and imperial quantities are alternate measurements, so use one system rather than adding both. If you change the yield, keep the pan size and thickness of the food in mind: a crowded pan steams food and a deep baking dish can extend the cooking time.

Equipment

Set out large saucepan, frying pan, 2 litre baking dish, colander. A wide pan gives moisture somewhere to evaporate; for an oven dish, leave space between pieces so heat can circulate. Use separate board and knife surfaces for raw protein and foods that will be eaten without further cooking.

Ingredients

You will need: penne: 350 g (12 oz); onion, thinly sliced: 200 g (7 oz); baby spinach: 150 g (5 oz); butter: 30 g (2 tbsp); plain flour: 30 g (¼ cup); milk: 600 ml (2½ cups); mature cheddar, grated: 250 g (9 oz); Dijon mustard: 10 g (2 tsp); breadcrumbs: 50 g (1¾ oz). Gather the ingredients before heating the pan so the aromatics do not burn while a measurement is being found.

• penne — 350 g / 12 oz
• onion, thinly sliced — 200 g / 7 oz
• baby spinach — 150 g / 5 oz
• butter — 30 g / 2 tbsp
• plain flour — 30 g / ¼ cup
• milk — 600 ml / 2½ cups
• mature cheddar, grated — 250 g / 9 oz
• Dijon mustard — 10 g / 2 tsp
• breadcrumbs — 50 g / 1¾ oz

Method

Read the full method once, then prepare the ingredients in the order listed. Keep raw and ready-to-eat ingredients separate, and wash hands and equipment after raw-protein contact.

Step 1

Heat the oven to 200°C/400°F. Cook penne for 2 minutes less than its packet time, then drain.

Step 2

Cook onion in half the butter until golden; add baby spinach and stir until wilted.

Step 3

Melt remaining butter in a saucepan, stir in plain flour for 1 minute, then gradually whisk in milk. Simmer until thick, then stir in 200 g (7 oz) mature cheddar and Dijon mustard.

Step 4

Combine penne, onion, spinach and cheese sauce in the baking dish. Top with breadcrumbs and remaining mature cheddar.

Step 5

Bake for 20 minutes until bubbling and golden, then rest for 5 minutes.

Cooking and safety check

Bake until the centre is steaming hot and the pasta is tender. A time estimate and a browned surface do not prove that the centre is cooked. Use a suitable food thermometer where the ingredient or local guidance requires one, and follow the package or official instructions for the specific food.

Substitutions that respect the dish

A substitution should preserve the recipe’s job, not merely its colour. Use gluten-free penne and gluten-free breadcrumbs for a gluten-free bake. Use plant butter, unsweetened soy milk and dairy-free cheese for a milk-free version; soy is an allergen. Use kale instead of baby spinach, cooking it with the onion until tender.

• Use gluten-free penne and gluten-free breadcrumbs for a gluten-free bake.
• Use plant butter, unsweetened soy milk and dairy-free cheese for a milk-free version; soy is an allergen.
• Use kale instead of baby spinach, cooking it with the onion until tender.

Allergen notes

This recipe contains or may contain milk, gluten, mustard. Check every packaged ingredient because formulations and cross-contact warnings vary.

Common mistakes and how to correct them

Use one troubleshooting change at a time. If the centre is undercooked, return it to the appropriate heat and check again rather than relying on the outside colour. If the pan is dry, add liquid gradually; if it is watery, reduce uncovered. Texture may also reflect crowded equipment, a different ingredient size, or a changed batch quantity.

• Whisk milk in gradually to prevent flour lumps.
• Undercooking penne initially prevents soft pasta after baking.
• If the top colours too fast, cover loosely with foil.

Leftovers and storage

Refrigerate within two hours for up to three days. Reheat covered at 180°C/350°F until steaming hot.

Serving ideas

These sides and finishes suit baked cheese and onion pasta without changing the recipe itself.

• Green salad
• Steamed peas
• Pickled red cabbage

Frequently asked questions

Can I use leftover pasta?

Yes; omit boiling and add 60 ml (¼ cup) extra milk to the sauce.

Can it be frozen?

Freeze cooled portions for up to one month; thaw before reheating.

Related recipes and tools

Browse the related recipes for a different appliance, pace, or ingredient pairing. Use the serving scaler only after checking the stated yield, and use the storage guide before deciding whether to save a portion. Related links help with the next decision; they do not make this recipe suitable for every diet or kitchen.