Combine the cream, mascarpone, and vanilla seeds in a saucepan over medium to medium-high heat and cook until almost boiling, approximately 2 minutes.
Take the cream mixture off the heat and stir until smooth. Stir in the ginger.
Pour the cream mixture into a container, cover, and let steep in the fridge for 2 hours or up to overnight.
After the cream has finished steeping, preheat the oven to 300°F. Put 6 ramekins in a 9×13-inch baking dish. Bring a kettle of water to the boil.
Put the egg yolks and light brown sugar into a separate bowl.
Whisk until the yolks turn pale yellow and have slightly thickened.
Slowly pour the cream mixture into the egg yolks through a strainer, whisking the whole time.
Fill each ramekin with the crème brûlée mixture.
Pour hot water into the baking dish until it is halfway up the sides of the ramekins.
Bake for 20 minutes. The crème brûlées should be slightly jiggly, but not wet. If they are still not set, bake for another 5 minutes.
When set, remove crème brûlées from oven. Take them out of the water bath and let them cool to room temperature (approximately 30 minutes) before transferring them to the fridge to chill for at least 2 hours.
Once chilled, turn on the broiler. Sprinkle 1 teaspoon of granulated sugar on top of each ramekin.
Put the crème brûlées under the broiler (or use a kitchen torch) to melt the sugar until it caramelizes into a crispy shell.