In a small saucepan over medium-low heat, stir together the cream, Port, maple syrup, and brown sugar and heat until the mixture comes to a bare simmer.
Meanwhile, in a medium glass dish such as a pie plate, combine the butter, chocolate, and salt.
Pour the warm cream mixture over the chocolate mixture and let it sit for a couple minutes. Stir gently until the chocolate melts completely and the mixture is smooth.
Refrigerate, uncovered, until the chocolate mixture is firm, at least 2 hours and up to overnight.
Line a resealable container with parchment paper and place it near your work surface. Sift the cocoa powder into a small, shallow bowl.
Using a 1 1/2 teaspoon cookie dough scoop or 2 small spoons, scoop up a small amount of the chocolate mixture and quickly roll it between your palms into a ball about 3/4 inch (2 cm) in diameter.
Gently drop the truffle into the cocoa powder, turn to coat it evenly, and then place it in the prepared container. You can keep the truffles in a covered container in the fridge for up to 3 weeks.
Let sit at room temperature for 15 minutes before serving.
