6: Prepare the spice mixture: mix in a cup 1 teaspoon curry powder, 1 tablespoon mustard seeds, 1 teaspoon cumin seeds and 1 teaspoon mustard powder. Preheat the oven to 390°F (200°C)
7: Use a casserole or skillet that can go both on the hob and in the oven. Put on high heat and pour in 3 tablespoons olive oil. When good and hot the chopped onion, salt and pepper. Cook for 1 or 2 minutes without colouring.
8: Add the spice mixture and turn down the heat. Cook for 1 or 2 minutes, stirring constantly.
10: Add the cauliflower, mix well and cook like this for 1 or 2 minutes.
11: Scatter the gratin topping over...
12: ...and brown in the oven for about 15 minutes (finish under the grill if necessary).
Remarks
You can vary the spice mixture, but do keep mustard (both seeds and powder) as the basis and add your preferred spices to this. If you don't have any mustard powder, use double the weight of mustard paste.