Turn your slow cooker on to low and allow to heat for 15 minutes or so.
Meanwhile add the butter, chopped brown onion and garlic to a frypan and saut until onion goes clear.
Transfer to slow cooker and add the rice and mix to coat.
Pour in the stock and white wine.
Cook on low for 2 hours.
Stir well.
Add the additional ingredients you'd like to flavour your risotto with (mushrooms and chicken is nice, or pumpkin and spinach -add spinach just prior to serving though) and allow to cook for a further 1 hour or until all stock is absorbed- this will depend on your slow cooker
Stir through the cheese, and serve immediately.
This freezes and reheats well.
Tip- it is best to precook meats prior to adding so that the juices don't ruin the mix