Preheat the oven to 325˚. Bring the heavy cream and vanilla seeds and pod to a simmer in a medium saucepan over medium-high heat. Remove from the heat and let sit 15 minutes; remove the vanilla pod.
Make the custard: Whisk the egg yolks, maple syrup, sugar, maple extract and salt in a medium bowl until smooth. Gradually add 1/2 cup of the warm cream mixture, whisking constantly until combined. Whisk in another 1/2 cup, then whisk in the rest. Strain through a fine-mesh sieve into a large liquid measuring cup.
Set four 6-ounce ramekins in a large roasting pan; divide the custard among the ramekins. Carefully pour boiling water into the roasting pan so it comes halfway up the sides of the ramekins. Cover the roasting pan with foil and carefully transfer to the oven. Bake until the custard is set but the centers still jiggle slightly, 30 to 40 minutes. Uncover and remove the ramekins from the water bath; transfer to a baking sheet and let cool to room temperature. Refrigerate until chilled and set, at least 2 hours or overnight.
Working with one ramekin at a time, sprinkle the custard with 1 to 2 teaspoons sugar and melt with a kitchen torch, moving the flame back and forth over the sugar until melted. Let harden, about 5 minutes.