ooo good one :)
I found a good Roux method for this the other day, but without the onions and chilli. It did have a teaspoon of mustard as it's secret ingredient though which made the difference. oh and it wanted the lot to be baked for 20 mins at the end, whereas grilling is probably a better idea!

I tried cheating and microwaving a cornflour one, but discovered that the cooking the cauliflower separately really is a necessary part of the thing! Still cauliflower is edible raw so it didn't really matter...