For the sausages, place the cheese, breadcrumbs, onions, thyme, parsley, eggs, egg yolks, milk and garlic into a large bowl. Season well with salt and freshly ground black pepper, then mix your hands to combine the ingredients well.
Place the sausage mixture into the fridge to chill for 2-3 hours, then remove and mould it into sausage shapes. (You should get about 12 normal-sized sausages from this quantity of mixture, depending how big you like your sausage.)
Heat the oil in a deep frying pan until a breadcrumb sizzles and turns brown when dropped into it. (CAUTION: hot oil can be dangerous. Do not leave unattended.)
Carefully add the sausages to the oil and fry them, turning if necessary, for 4-5 minutes, or until golden-brown, then remove with a slotted spoon and drain onto kitchen paper. (NB: you can also shallow fry or grill the sausages.)
For the potatoes, melt the butter in a separate frying pan. Add the potatoes and sauté for 4-5 minutes, or until crisp and golden.
To serve, place a few sausages onto each plate with a large spoonful of sautéed potatoes alongside. Add a dollop of tomato chutney or ketchup.