Vitamin B9 (folate) from natural foods can be considered equivalent to methyl folate, since this is the form in which it is mainly present. This is significant, since methylfolate enters the bloodstream in its unchanged form, whereas folate must first be converted by the liver. Among foods of animal origin, liver and eggs are the most abundant in folate, and among plant foods, green vegetables and pulses are rich in folate. Adequate folate intake during pregnancy helps reduce the incidence of premature birth and anaemia in pregnancy. Chicken liver has 588 mcg/100 g and boiled eggs 44 mcg/100 g of vitamin B9.

Melt the duck fat in a large frying pan, carefully add the onion and cook over a low to medium heat. Prepare the liver carefully and cut it into similar sized pieces so that it is evenly cooked later. When the onions are soft and light golden brown (after about 10 minutes), add the liver. Be careful and use a splatter-proof sieve. Turn the liver over after 4-5 minutes to cook the other side. Then season with salt and pepper. Fry for about 10 minutes in total, sprinkle with basil and set aside to cool. Hard-boil the eggs (they will cook in 7-8 minutes in boiling water). Then cool them in cold water and peel them. In a food processor, combine the onion, the liver in duck grease, and the eggs and mustard, and process for a relatively long time, about 3-5 minutes. The longer you puree, the creamier the end result will be. Taste before removing and season with salt, pepper or mustard if necessary.