Place the chipolatas into a large frying pan over a medium heat and fry, turning occasionally, for ten minutes, or until browned on all sides.
Add the onions and fry for 5-10 minutes, until they are soft and evenly browned.
Place the stock into a saucepan over a medium heat and bring to the boil.
Add the marmalade to the stock. Stir to dissolve the marmalade, then reduce the heat to simmer for ten minutes, or until reduced in volume by half.
Check the sausages are completely cooked through, then add the marmalade stock mixture to the sausages pan.
Cook together for 2-3 minutes to absorb flavour.
Pour off any excess liquid from sausages. Secure a sausage to each slice of toast with a cocktail stick and garnish with a spoonful of the caramelised onion.
Serve with a dollop of American-style mustard.