Place the tuna in a food processor and pulse to break up the fish. With the machine running, add the butter, balsamic vinegar, and soy sauce and blend until smooth. Then stop the machine and scrape down the sides of the processor bowl. Add the lemon juice and pulse again. Season, to taste, with salt and pepper and blend again. Check the seasoning, then add the heavy cream and pulse to blend. NOTE: Be careful not to over blend once the cream is added or the mixture may break.
Serve at room temperature, or cover and refrigerate for up to 4 days.
If refrigerated, return the spuma to room temperature before serving.
Serve with breadstick, crostini, or crackers to spread it on. Also excellent served with champagne.
Italian Tuna Mousse Recipe - Spuma Di Tonno: https://whatscookingamerica.net/appetizers/spumatunamousse.htm