For the custard, combine almond milk and heavy cream in a medium saucepan over medium heat. Stir in granulated erythritol or sugar and cook, stirring continuously until cream mixture begins to steam but does not boil, and reaches 175F on an instant read thermometer.
In a medium bowl, whisk egg yolks until smooth. Slowly whisk in about 1 cup of the hot cream to temper the yolks. Once combined, slowly whisk egg yolk mixture back into saucepan. Continue to cook, stirring constantly, until mixture reaches 180 to 185F on an instant read thermometer. Custard should be thick enough to coat the back of a wooden spoon. Stir in stevia extract, if using.
Pour custard into a bowl set over an ice bath and let cool 10 minutes. Then cover tightly with plastic wrap and chill in refrigerator for at least 3 hours.
For the sauce, combine strawberries, rhubarb, erythritol or sugar and 2 tbsp water in a medium saucepan over medium heat. Cook until berries release their juices and fruit is easily mashed with a fork, 5 to 10 minutes. Off heat, mash the fruit, leaving some chunks if you like. In a small bowl, whisk together remaining 2 tsp water and arrowroot or corn starch. Stir into fruit mixture and return to heat until sauce is thickened, about 3 minutes. Let cool.
Take about 2 cups of strawberry rhubarb sauce and toss with 2 tbsp vodka. This step is optional but will help reduce iciness in your ice cream.
When custard is chilled, stir in vanilla extract. Pour into canister of an ice-cream maker and churn according to manufacturer’s directions. In the last 5 minutes of churning, pour half of the strawberry rhubarb sauce into the ice-cream maker.
When fully churned, transfer ice cream to an air-tight container. Swirl in remaining rhubarb sauce. Cover with plastic wrap flush to the surface and freeze until firm, about 2 to 3 more hours.