In a medium bowl, combine dulce de leche and 1/4 cup of the heavy cream and beat until smooth.
In a large bowl, combine remaining heavy cream and vanilla extract. Using a handheld electric mixer, beat cream, starting on low, working up to high, until stiff peaks form (when you lift the beaters out, the peaks of cream should stand straight up without flopping over).
Use a rubber spatula to fold in about 3/4 of the dulce de leche (reserve 1/4 to swirl in at the end), being careful not to deflate the whipped cream too much.
Scoop half of the whipped cream mixture into a loaf pan or freezer container. Spoon half of the reserved dulce de leche over the top and use a knife to swirl the mixture into the cream.
Add remaining whipped cream and repeat with remaining dulce de leche. Cover pan with cling wrap or lid and freeze until solid, at least 6 hours, preferably overnight.
Serve and enjoy!