When ready to cook, start the Traeger grill on Smoke with the lid open until the fire is established (4 to 5 minutes).
Put the 6 tablespoons of Sugar in the Raw in a clean coffee or spice grinder and grind until the coarse crystals are fine. Set aside.
Pour the cream into a medium saucepan. Split the vanilla bean and scrape out the pulp and seeds; add both to the cream. Or stir the vanilla extract into the cream. Add the Grand Marnier, if using. Bring to a boil over medium-high heat. Remove from the heat and let cool for 15 to 20 minutes. Strain into a large pitcher with a spout. Reserve the vanilla bean for another use.
In the meantime, make the custard: Add the egg yolks and 3/4 cup of granulated sugar to a large mixing bowl. Using a stand mixer or hand-held electric mixer, beat the egg yolks and sugar with the whisk attachment until they are a pale yellow, about 2 minutes. Very slowly add the cream with the mixer running continuously on medium-low speed. If you add the cream to the egg yolks too quickly, the eggs will scramble and your custard will not be silky-smooth. Put a fine-mesh strainer over the mouth of the pitcher and pour the custard mixture through it.
Arrange six 7- to 8-ounce heatproof ramekins on a large rimmed baking sheet or in a cake pan. Divide the custard among the ramekins. Carefully set the pan with the ramekins on the grill grate of your Traeger. Pour enough hot water into the pan to reach halfway up the sides of the ramekins. Smoke the creme brulees for 15 minutes. Increase the heat to 325F and continue to bake the creme brulees until they are set, 40 to 45 minutes depending on the depth of the ramekins. Custard in deeper ramekins will take longer to cook.
Let the creme brulees cool, then cover with plastic wrap and refrigerate for at least 3 hours, or until well-chilled and firm.
Remove from the refrigerator 30 minutes before serving. Just before serving, evenly dust the top of each creme brulee with the reserved raw sugar.
Using a small kitchen torch, melt and caramelize the sugar, moving the torch constantly, until the sugar's crisp and golden brown. Top with berries and mint and serve immediately.