Prepare the Mousse Base: Place the dulce de leche in a mixing bowl. Add a pinch of salt for a balanced caramel flavor, if desired.
Whip the Cream: In a separate bowl, pour the cold double cream. Using an electric mixer, whip the cream until it begins to thicken but is still soft (do not overwhip).
Combine the Ingredients: Add the cornflour to the whipped cream and mix gently for 10-15 seconds to combine. The cornflour helps stabilize the mousse. Gradually fold the whipped cream into the dulce de leche using a spatula. Be gentle to maintain the light, airy texture. Fold until fully incorporated and smooth.
Chill the Mousse: Spoon the mousse into serving glasses, ramekins, or bowls. Smooth the tops with the back of a spoon. Place the mousse in the refrigerator and chill for at least 1 hour to set. For a firmer texture, chill for up to 2 hours.
Serve and Garnish: Before serving, drizzle extra dulce de leche over the top for added indulgence. You can also garnish with a sprinkle of sea salt, chocolate shavings, or a dollop of whipped cream for an elegant presentation.