1Place the 1500g veal head in a large pot with 200g carrot, 100g celery, 150g leek, 150g onion, 20g salt, 5g peppercorns, 2g bay leaf, and 5g thyme.
2Cover with water, bring to a simmer, and perform dépouillage by skimming impurities from the surface until the veal is tender.
3Mash the 70g hard-boiled egg yolks in a bowl with 30g Dijon mustard, 40g wine vinegar, and 3g salt until smooth.