01 -
Prepare your ice cream maker according to manufacturer instructions. This may require chilling your maker in the freezer overnight.
02 -
Preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper or a silicone baking mat.
03 -
Combine butter, flour, oats, brown sugar, cinnamon, nutmeg, and salt in a bowl. Rub the butter into the dry ingredients to form large crumbles.
04 -
Spread the crumbles on the prepared baking sheet and bake for 8-10 minutes until golden. Allow to cool completely.
05 -
In a bowl, whisk together egg yolks and half the sugar until well combined.
06 -
Create an ice bath with plenty of ice in a large bowl for cooling the custard later.
07 -
In a medium saucepan, combine remaining sugar, cream, milk, and salt. Heat until steaming and gently simmering at the edges, but do not allow to boil.
08 -
While whisking the egg yolks vigorously, slowly drizzle in half of the hot milk mixture. Then, whisk the remaining milk in the saucepan and gradually pour the egg mixture back into the saucepan.
09 -
Continue stirring the mixture over medium-low heat until it thickens enough to coat the back of a spoon. Remove from heat and stir in vanilla, rosewater (if using), and rhubarb jam.
10 -
Place the saucepan in the prepared ice bath, being careful not to get water into the custard. Cool completely.
11 -
Transfer the cooled custard to a gallon freezer bag and refrigerate until completely chilled, at least 4 hours or preferably overnight.
12 -
Pour the chilled custard into your ice cream maker. You may need to work in batches for optimal results. Churn according to manufacturer instructions, drizzling in the creme fraiche as it churns. Add the crumble during the final minute of churning.
13 -
Transfer the churned ice cream to airtight containers and freeze until solid, at least 4 hours before serving.