Cut the cauliflower into small florets.
Bring a large pot of water to boil.
Add a pinch of salt to the water.
Boil the cauliflower for 5-6 minutes.
It should be tender but still firm.
Drain well and set aside in your baking dish.
Melt butter in a medium saucepan over medium heat.
Add flour and whisk for one minute.
This creates a smooth paste called roux.
Slowly pour in the milk while whisking constantly.
Keep stirring to avoid lumps forming.
Cook until the sauce thickens (about 5 minutes).
The sauce should coat the back of your spoon.
Remove the saucepan from heat immediately.
Stir in 1.5 cups of shredded cheddar cheese.
Add salt, pepper, and mustard powder now.
Mix until the cheese melts completely.
The sauce should be smooth and creamy.
Taste and adjust the seasoning if needed.
Preheat your oven to 375°F (190°C).
Pour the cheese sauce over the cauliflower florets.
Make sure all pieces are well coated.
Sprinkle remaining cheese on top evenly.
Add breadcrumbs for extra crunch if you like.
Bake for 20-25 minutes until golden and bubbly.
The top should be beautifully browned.
Let it cool for 5 minutes before serving.
This helps the sauce set a little.
Serve hot as a side or main dish.
Enjoy your homemade cauliflower cheese!