Melt 2 T of butter in sauté pan over medium heat. Add onion, cilantro, garlic, and ginger and sauté for 2 to 3 minutes or until mixture is fragrant. Add mushrooms and soy sauce, sauté for 4 to 5 minutes or until liquid reduces slightly; remove from heat and allow to cool. Whip remaining butter in a medium-sized mixing bowl until smooth and light. Add reduced mixture and lime juice to butter and mix until well combined. Remove butter from bowl and spoon onto parchment paper. Roll into a log, using edge of baking sheet to form a tight log. Chill for 2 hours before serving.