Preheat oven to 200°C (400°F).

Place rhubarb, 2 tbsp sugar and grated ginger on a baking sheet.

Roast for 20 minutes, or until rhubarb is tender.

Let cool.

In a blender, puree the roasted rhubarb mixture until smooth.

In a saucepan, heat heavy cream, whole milk, and 150g sugar over medium heat until sugar dissolves.

In a separate bowl, whisk egg yolks.

Gradually whisk hot cream mixture into egg yolks.

Return mixture to the saucepan and cook over low heat, stirring constantly, until it thickens slightly (about 5-10 minutes).

Do not boil.

Strain the custard through a fine-mesh sieve into a bowl.

Stir in vanilla extract and cooled rhubarb puree.

Chill in the refrigerator for at least 4 hours, or overnight.

Churn the chilled mixture in an ice cream maker according to the manufacturer's instructions.

Freeze for at least 2 hours before serving.