Position a rack in the center of the oven and preheat to 300 degrees F. Place four 9-ounce ramekins in a roasting pan. Bring a large pot of water to a boil and keep hot until ready to use.
Set aside 12 of the raspberries and cook the rest with 1/2 cup of the sugar in a small saucepan over medium-high heat until the sugar has dissolved, the berries have broken down completely and the mixture starts to thicken, about 10 minutes. Let cool completely.
Put the cream, half-and-half and salt in a medium saucepan. Split the vanilla bean in half lengthwise, scrape out the seeds with the back of a paring knife and add them, along with the bean, to the cream mixture. Bring the mixture to a boil over medium-high heat; immediately remove from the heat, cover and set aside.
Combine the egg yolks with the remaining 1/2 cup of sugar in a large bowl and whisk until the mixture is pale yellow and thick. Whisking constantly, slowly pour in the hot cream mixture until well combined. Pour the custard through a fine-mesh strainer into a clean medium bowl and discard the vanilla bean.
Spoon 2 tablespoons of the raspberry coulis into each ramekin and spread to cover the bottom. Carefully ladle the custard into the ramekins, dividing evenly, and place the roasting pan in the oven. Carefully pour the hot water into the roasting pan until it reaches about 2/3 of the way up each ramekin. Bake until the custard is just set and still slightly jiggles, about 55 minutes. Immediately transfer the ramekins to a rack to cool to room temperature, then chill, uncovered, for 3 hours up to 2 days.
Just before serving, place the ramekins on a rimmed baking sheet and sprinkle sugar (about 1 tablespoon) over the top of each custard, tilting to spread evenly. Wipe off the ramekins with a moist paper towel. Using a torch, carefully caramelize the sugar until it is melted and a deep golden color. Once the sugar has hardened, garnish each custard with 3 of the reserved raspberries and serve.