Cut the butter into cubes and melt it in a saucepan over low heat. Remove from the heat and set aside for a few minutes to cool and to allow the milky solids to sink to the bottom. Carefully pour off the oily part, or clarified butter, leaving the milky solids behind. Let the clarified butter cool to room temperature.
In 2 or three batches, put the salmon cubes, clarified butter, and cream in the bowl of a food processor, and puree until fluffy and completely smooth. Transfer the salmon puree to a large bowl and stir in the herbs and lemon juice to taste. Chill before serving.