Soup: cut Tilsiter into 4 pieces, cover and let stand at room temperature for around 30 minutes.
Heat butter, sauté onions, then add diced pumpkin and potato and sauté for around 3 minutes. Pour in unfermented fruit juice and broth, cover, then let simmer at medium heat for around 25 minutes. Purée soup and season to taste.
Pour soup into bowls, add Tilsit pieces and let melt. Serve soup garnished with parsley.
Crostini: mix Tilsit with pumpkin seeds and sugar then season to taste. Place baguette slices on a baking tray lined with baking paper and top with cheese pieces.
Baking: 5-10 minutes in the middle of an oven preheated to 220 °C. Serve Tilsiter crostini with soup.