Braai the boerewors over hot coals until the exterior is well caramelised but the wors is still pink in the middle. Let the wors cool then slice it into discs. 

Mix the two cheeses together in a bowl. Lay the bread slices out and brush with butter. Spread a layer of chutney on six of the slices of bread and add slices of boerewors. Top the wors with sliced onion and a generous amount of cheese. Close the broodjies and brush the top of each with butter. 

Load the broodjies into a sandwich grid then close the grid and place the butter-brushed side down over medium heat coals. Brush the unbuttered side with the remaining melted butter. Braai slowly for a few minutes per side until they are evenly golden all over and the cheese is melted. To serve, slice each broodjie in half and serve with extra chutney for dipping.