Preheat the oven to 425°F (220°C).

Line a baking sheet with parchment paper and place the marrow bones on it.

Roast for 30-35 minutes until the marrow is soft.

Remove from the oven and allow to cool until you can handle them comfortably.

Scoop out the marrow and place it into a fine mesh strainer to drain excess fat.

Reduce the oven temperature to 325°F (165°C).

Place 3-4 ramekins in a rimmed baking dish.

In a high-speed blender, combine the drained marrow, raw milk, honey or maple syrup, egg yolks, vanilla extract, and sea salt.

Blend until the mixture is smooth and well combined.

Pour the custard mixture into the prepared ramekins.

Pour hot water into the baking dish until it reaches halfway up the sides of the ramekins, creating a water bath.

Carefully transfer the baking dish to the preheated oven.

Bake for 45-55 minutes, or until the custards are set and the tops have formed a crust.

Remove the ramekins from the water bath and allow them to cool to room temperature.

Transfer to the refrigerator to cool completely before serving