In a bowl, soak the livers in the milk for 2 hours. Drain well.

In a large saute pan, melt 4 tablespoons of the butter over medium -high heat. Add the onions and cook, stirring, until soft, about 3 to 4 minutes. Add the garlic and cook until fragrant, about 30 seconds. Add the duck livers, thyme, salt and pepper and cook, stirring, until the livers are browned on the outside and still slightly pink on the inside, about 5 minutes. Add 1/2 cup Armagnac or brandy and cook until most of the liquid is evaporated and the livers are just cooked through.

Remove from the heat and let cool slightly.

In the food processor, purée half of the liver mixture. Add half of the remaining butter and pulse to blend. Using a rubber spatula, scrape the purée into a bowl. Repeat with the remaining livers and butter and add to the bowl. Taste and season if necessary. Set a fine mesh sieve or tamis over a bowl, and pass the purée through it by scraping small amounts over the mesh surface with a plastic bench scraper. Discard any solids.

In a separate bowl, whip the heavy cream to soft peaks. Add the remaining 2 tablespoons of Armagnac to the cream and mix well. Fold the whipped cream into the purée.

Line a 6 cup terrine with plastic wrap. Pour the liver purée into the terrine, cover with plastic wrap, and refrigerate for at least 6 hours to set. Alternately, you may pour the purée into individual ramekins.

To remove the pate from the terrine, invert it onto a cutting board and carefully remove the plastic wrap.

Slice the terrine, garnish with parsley, serve with toast points and mustard fruits.

Serve the terrine with toast points, crackers, or crusty bread, garnished with the parsley and with any mustard fruits or fruit jam if desired.