1. Marinate the chicken livers for 24 hours with 200 ml of port and the bouquet garni.

2. The next day, drain the livers. Reserve the liquid and discard the bouquet.

3. In a pan, cook the onion and garlic in the duck fat. Add the marinated chicken livers and continue cooking over high heat for 4 minutes, then remove from heat and reserve.

4. Deglaze the bottom of the pan with the port used previously for marinating and reduce by half.

5. Transfer everything to a food processor, add the softened butter and cream, and mix for 2 minutes. Pass the mixture through a fine sieve and season.

6. Pour the mixture into glass jars and refrigerate for 2 to 3 hours.