In a heavy 2-quart saucepan over medium heat, bring the heavy cream and oyster liquor from the oysters to a simmer. Remove from the heat.
Meanwhile, in a large saute pan over medium heat, melt the butter. Add the celery and a pinch of the salt and sweat for 3 to 4 minutes. Add the onion and continue cooking until translucent, about 4 to 5 minutes. Add celery seed, hot pepper sauce, and oysters and cook for 1 to 2 minutes, or until the edges of the oysters start to curl.
Transfer the oysters to the carafe of a blender and add enough of the cream just to cover.*
Puree until the mixture is smooth. Return the remaining cream to medium heat, add the pureed mixture, and cook until heated through.
Just before serving, add the lemon juice, chopped herbs, and season with salt and pepper, to taste.
*When blending hot liquids: Remove liquid from the heat and allow to cool for at least 5 minutes. Transfer liquid to a blender or food processor and fill it no more than halfway. If using a blender, release one corner of the lid. This prevents the vacuum effect that creates heat explosions. Place a towel over the top of the machine, pulse a few times then process on high speed until smooth.