1. Heat milk, salt, and sugar in a saucepan
2. In a separate bowl, stir together the egg yolks
3. Reheat milk, then temper yolks by gradually pouring some milk into the yolks, whisking constantly, then pour the warmed yolks and milk back into the saucepan
4. Cook over low heat, stirring constantly and scraping bottom with heat-resistant spatula, until custard thickens enough to coat spatula
5. Combine ice cold heavy cream and rhubarb purée in large bowl over a bed of ice
6. Strain custard into cream and rhubarb purée mixture; stir over ice bath until cool
7. Refrigerate to chill thoroughly: preferably overnight
8. Freeze in ice cream maker according to manufacturer’s instructions

Instructions for using the Thermomix:

1. Weigh milk, salt, and sugar into TM bowl; heat on 50°C for 10 minutes at speed 2-3
2. Set time for 15 to 18 minutes, temperature to 80°C and speed on reverse 2-3; add each of the yolks to the warmed milk one at a time through hole in lid, within first 2 minutes
3. Combine ice cold heavy cream and rhubarb purée in large bowl over bed of ice
4. Strain custard into cream and rhubarb purée mixture; stir over ice bath until cool
5. Refrigerate to chill thoroughly: preferably overnight
6. Freeze in ice cream maker according to manufacturer’s instructions