Wrap the potatoes in aluminum foil and cook in the oven at 250 ° C for 1 hour until they are soft. Remove the aluminum foil and place the potatoes in the oven for another 10 minutes.
While the potatoes are in the oven, you can dice the cheese, cut the chives and grate the parmesan.
Halve the potatoes and hollow them out, leaving an edge of about 1 cm. Mix the loosened inside of the potatoes with the butter, cream, parmesan and mustard. Then fold in the cheese cubes and chives. Now put the mixture back into the potatoes and bake the potatoes at 220 ° C for another 10-15 minutes. As soon as they are nice and brown, they can be served.