Fill a 3 quart pot with 2 quarts of water and place on stove over HIGH heat. Once water comes to a boil, add onion, bay leaf, salt, pepper and pork feet. Boil until pork feet have cooked through (approximately 1 hour).
Once pork feet have cooked through, remove from pot and place on cutting board. Once pork feet are cool enough to touch, debone and chop into small pieces.
Place chopped pork feet on plastic wrap and roll into a cylinder shape. Ensure the cylinder is wrapped tightly and place in refrigerator to chill overnight.
When ready to serve, remove from refrigerator and remove plastic wrap. Slice thinly and arrange on a flat plate.
In a small bowl, toss chopped walnuts, oil, salt, pepper, and vinegar. Drizzle vinaigrette over sliced pork carpaccio and finish with toasted pine nuts and chopped chives.