Peel and slice onions. Peel and dice potatoes. Mince garlic. Heat chicken fat over medium heat, add onions and cook till soft but not brown. Add garlic, potatoes, herbs, pepper and stock. Simmer 1 hour. Add cream. Purée with a hand blender adding butter while pureeing. Season with salt as needed.
Whisk together ricotta, salt, white pepper, and truffle oil. Pipe on top of soup in bowl. Garnish with cooked bacon pieces. Serve with Ravines 2013 Chardonnay (learn more here).