Scrape down the sides and add the smoked salmon, lemon juice, capers, fresh dill, scallion, salt, pepper and Tabasco Sauce, if using. Secure the lid and run on low for another 1 to 2 minutes, stopping to scrape down the sides, as needed. Once the mousse is fluffy and well-combined, transfer it to a bowl or a piping bag fitted with a star tip.