Using an electric mixer on medium-low speed, beat 3 cups cream, 3 Tbsp. powdered sugar, and salt in a large bowl until soft peaks form. Spread a thin layer of whipped cream on base of springform pan. Top with a single layer of cookies (if using a plate, arrange inside a 9″ circumference). Continue layering cream and cookies, ending with a layer of cream, until all cookies are used (you should have 8 layers). Cover loosely with plastic wrap and chill at least 6 hours or up to overnight. Using electric mixer on high speed, beat remaining 1 1/2 cups cream and 1 Tbsp. powdered sugar in a large bowl until soft peaks form. If using, fit pastry bag with tip; transfer whipped cream to bag. Pipe cream all over top and sides, or use a spatula to frost top and sides of cake with cream. Cake can be made 1 day ahead. Cover and chill.