01 - 
                Pour lukewarm milk into a measuring jug, sprinkle the active-dry yeast over the surface, and let stand for 5–10 minutes until slightly foamy.
              
              
              
                02 - 
                In a large mixing bowl, combine all-purpose flour, granulated sugar, and salt. Using a stand mixer or dough hook, add the yeast-milk mixture to the dry ingredients and mix until a dough begins to form.
              
              
              
                03 - 
                Gradually pour in vegetable oil, 2 tablespoons at a time, mixing thoroughly after each addition. Continue mixing for 3–5 minutes until the dough is smooth and elastic.
              
              
              
                04 - 
                Shape the dough into a ball and place in a buttered bowl. Cover with a cloth and allow to rise in a warm environment for 1 hour.
              
              
              
                05 - 
                Melt butter in a saucepan over medium heat. Add flour and a pinch of salt; cook, stirring frequently, until pale golden. Gradually whisk in the milk in two additions, stirring until smooth. Continue cooking, whisking constantly, until the sauce boils and thickens, about 7 minutes. Lower heat, simmer 10 minutes, and season with freshly cracked pepper and ground nutmeg if using. Remove from heat and set aside.
              
              
              
                06 - 
                Punch down the risen dough on a lightly floured surface. Roll it into a large rectangle, approximately 30 x 40 cm. Spread béchamel sauce over half the rectangle lengthwise. Arrange ham slices and sprinkle with grated Swiss cheese over the sauce.
              
              
              
                07 - 
                Fold the dough over the filling, pressing the edges firmly to seal. Cut the filled dough into 8 equal pieces using a sharp knife.
              
              
              
                08 - 
                Arrange the portions on a parchment-lined baking sheet. Loosely cover with a damp cloth (do not let it touch the dough) and allow to proof for 1 hour in a warm place.
              
              
              
                09 - 
                Preheat oven to 180°C. Brush the tops of the buns with milk or beaten egg yolk and sprinkle with additional grated cheese if desired. Bake for 20–25 minutes until golden brown. Cool briefly on a rack and serve warm.