01 -
Place the peeled and quartered onion in a blender and pulse for 2 seconds at speed 5. Scrape down the sides with a spatula.
02 -
Add butter, flour, semi-skimmed milk, egg yolk, salt, pepper, and nutmeg to the blender. Cook for 8 minutes at 90°C, speed 4, until the sauce thickens.
03 -
Add 100 grams of grated Emmental to the sauce. Blend for 1 additional minute at 90°C, speed 4, until smooth.
04 -
Grease a baking dish with butter and spread a thin layer of Mornay sauce over the base. Arrange one layer of lasagna sheets, trimming as needed.
05 -
Spread one-quarter of the Mornay sauce onto the pasta. Add 2 slices of ham and one-third of the raclette cheese slices evenly.
06 -
Place another layer of lasagna pasta, then distribute one-third of the remaining sauce, 2 more ham slices, and additional raclette cheese.
07 -
Repeat the process with pasta, half of the remaining sauce, the final 2 slices of ham, and the rest of the raclette cheese.
08 -
Finish with a final layer of lasagna sheets and the remaining Mornay sauce. Sprinkle the top with 40 grams of Emmental cheese.
09 -
Preheat oven to 200°C. Bake for 20 minutes until the surface is golden and bubbling.