- In large frying pan, melt 2 tbsp of the butter over moderate low heat.
- Add onions and cook until soft, about 5 minutes.
- Add garlic and cook for 1 minutes. longer.
- Transfer to food processor or blender.
- Melt remaining 4 tbsp butter in same pan.
- Add livers and saute' over med-high heat, tossing until browned outside but still rosy inside, 3 to 5 min.
- Sprinkle with salt, thyme, tarragon, pepper and cognac. Cook 1 minute scraping bottom of pan.
- Scrape liver and pan juices into food processor.
- Purée until smooth. scrape into serving bowl or crock.
- Let cool to room temp then cover and refrigerate until cool/several hours.