Step 1

Add the sourdough starter (or discard) and butter to the saucepan. Whisk together until they form a thick paste (roux).

Step 2

Place the pan on a low heat and gently cook the roux.

Step 3

Now add 100g of warm milk. Whisk continuously until the milk starts to thicken. It should be smooth without too many lumps.

Step 4

Keep whisking and add 100g more milk.

Step 5

Once the sauces starts to thicken again, add the remaining 200g of milk.

Step 6

Keep whisking until the sauce is silky smooth and thickened. Add nutmeg, salt and white pepper if desired.

Step 7

If you'd like add some cheese, add it once the sauce is cooked. Whisk vigorously until the cheese has melted through the sauce.

Step 8

Add sourdough starter, milk and butter to the jug. Add the egg now too if you are using.

Step 9

Set Thermomix at speed 4 - 90C - 7 minutes (make sure you have the measuring cup in place).

Step 10

Once the sauce is cooked, add cheese if desired and season with nutmeg, salt and pepper.