Line a 9X5 loaf pan with parchment paper and place it in the freezer to chill while you prepare the ice cream base.
Add the dulce de leche sweetened condensed milk and vanilla extract to a large bowl and stir to combine. Set aside.
Add the heavy cream to the bowl of a stand mixer fitted with the whisk attachment (or use a large bowl and an electric hand mixer).
Mix the heavy cream on medium-high speed until stiff peaks form.
Add the whipped cream to the bowl of dulce de leche and vanilla, and gently fold them together.
Transfer half of the ice cream base to the chilled loaf pan and smooth it out into an even layer.
Drizzle ¼ cup of dulce de leche on top of the ice cream layer, then use a butter knife to swirl it throughout the ice cream.
Add the remaining ice cream base to the loaf pan, and repeat the drizzling and swirling process with another ¼ cup of dulce de leche.
Cover the loaf pan with plastic wrap or foil and place it in the freezer to chill for at least 6 hours, although 12 hours is ideal.
Once the ice cream is firm, serve and enjoy.