Simple to make but super delicious to eat, this cheesy gratin comes together is amplified by the flavour of leeks. It's the perfect side dish to a special occasion meal!
Preheat oven to 190°C/375°F. Add the cauliflower florets to a steamer basket set over vigorously simmering water, ensuring the basket is not touching the water itself. Cover and steam for 8-10 minutes - until lightly tender but the florets still offer some resistance when pricked. Set aside. (See notes)
Add 25g (2 tbsp) of butter to a large skillet and set over medium heat. Once melted and beginning to foam, add one clove of the minced garlic and cook until very fragrant - about 30 seconds.
Add the breadcrumbs and cook, stirring constantly, until golden and toasted - about 3 minutes. Remove from the heat and stir in 25g (¼ cup) of the parmesan cheese and season with salt and pepper.
Add the remaining butter and 2 tbsp of olive oil to a large saucepan set over medium heat. Once shimmering and the butter is melted, add the leeks along with ¼ tsp of salt. Cook, stirring frequently, until the leeks are tender and beginning to brown around the edges - about 5-7 minutes.
Add the remaining garlic, nutmeg and a generous grind of black pepper and cook until very fragrant - about 30 seconds. Sprinkle over the flour and cook for a further 2 mintues.
Stirring constantly, slowly stream the milk into the leek mixture. Allow to come to a gentle simmer before removing from the heat. Off heat, stir in the cheddar cheese and parmesan cheese. Once the cheese is melted, gently fold in the cauliflower florets.
Scrape the mixture into an appropriately sized baking dish. Top with the toasted panko breadcrumbs. Set the dish on a rimmed baking sheet and bake until golden and bubbling - about 20-30 minutes. Allow to cool for 5 minutes before serving.
Notes
If you do not have a steamer, you can blanch the cauliflower in boiling water for 5 minutes. Drain and plunge into an ice bath immediately.