Step 1

Stir together the rhubarb, sugar, lemon juice, and a splash of water in a medium saucepan and bring to a simmer over medium heat. Let cook for about 15 minutes, stirring often, until some of the liquid has evaporated and the rhubarb is thick and soft. Be careful not to let it scorch on the bottom of your pan.

Step 2

Let the compote cool slightly then puree in a blender or food processor until completely smooth. Chill until cold.

Step 3

Meanwhile make the custard. Whisk the egg, yolks, sugar, and milk, making sure to break up the eggs completely. Heat the cream in a medium heavy bottomed saucepan until it starts to steam and gets little bubbles around the edge. Drizzle the hot cream into the egg mixture, whisking constantly. Pour the whole thing back into the pan and heat on medium, stirring constantly, until the mixture just starts to thicken. Do not bring it to a boil.

Step 4

Strain the mixture through a sieve, stir in the vanilla, and let cool. Chill until cold.

Step 5

Mix the cold rhubarb with the cold custard sauce and thoroughly blend. Pour into your ice cream maker and churn according to the instructions. Spread the soft ice cream into a container and freeze until scoopable.