Switch on the slow cooker and allow it to warm through.
Pop the butter into the slow cooker and allow it to melt.
Add mustard powder, mix together. Then sieve the flour into the butter. Mix quickly.
Add the garlic, salt and pepper. You should be left with a kind of thick paste now.
Pour in the double cream and quark and stir quickly and continuously to form a thick creamy sauce.
Next slowly add the milk bit by bit, stirring quickly. This will produce a must thinner but still creamy sauce.
Place the uncooked macaroni into the slow cooker, stir and ensure all of the liquid covers the macaroni.
Cover with a lid and cook on low for around 2 hours or until the macaroni is cooked al dente.
Remove the lid and stir in all of the grated cheese. Cover with the lid again and cook for a further 15 minutes.
Serve and enjoy.
Recipe note: If you prefer a crispier Mac and cheese. Retain a quarter of the cheese to sprinkle on the top and place into the oven for 10 - 15 minutes at the end.