Celery root mousseline with black truffle fondue and bitter cocoa

Mousseline:
2 pounds celery root
1 quart heavy cream
2 T butter, browned
4 each shallots sliced and sweated in butter
Celery salt to taste
1/2 T lemon juice
Salt & pepper to taste
Black Truffle Fondue:
1 Gallon pig`s foot stock
1/2 pound black Truffles
4 ounces Truffle juice
4 ounces butter
To taste salt and pepper
2 Tablespoons chopped black truffles
4 Tablespoons chopped chives

1. Mousseline: Peel celery root cut into large dice. Place in saucepan. Cover with heavy cream. Season with salt, pepper and celery salt. Cook until very soft. Drain and reserve the liquid. Puree in the blender with some of the reserved liquid and shallots to the consistency of the thick creme anglais. Add brown butter and lemon juice. Put through a fine chinois and strain again. Put in the espouma bottle with NO2 canister. Then pressurize.
2. Black Truffle Fondue: Reduce stock to 1 quart. Grate black truffles on box grater and add to stock. Add truffle juice, butter, salt and pepper. Blend until truffles are pureed. Set aside warm.
3. To Serve: Put truffle fondue on the bottom of espresso cup. Top with celery root mousseline. Dust with cocoa powder, chopped truffles and chopped chives.