Step 1

Preheat the slow cooker and when it's warm, pour in the melted butter.

Step 2

Sieve in the flour, stirring continuously to make a roux (see recipe notes), ensure any lumps of flour are smoothed out. Add the garlic granules, salt, pepper and mustard and mix through.

Step 3

Slowly pour in the double cream stirring continuously, to form a thick sauce. Then add the milk gradually (again stirring through) to create a thinner creamy sauce.

Step 4

Pour in the uncooked macaroni and make sure all of the pieces are submerged in the sauce. Cover and cook on low for 1.5 to 2 hours until the macaroni is cooked 'al dente' - when the pasta is soft but not bloated, and retaining its shape.

Step 5

Add the grated cheddar and parmesan cheese and stir through. Replace the lid and cook for a further ten minutes. Then serve immediately.