In a medium saucepot, combine cream, milk, and one tablespoon sugar. Set over medium heat and bring to a simmer. Stir as necessary to ensure milk does not burn along the sides or bottom of the pot.
Meanwhile, in a large bowl, whisk together egg yolks and remaining sugar. Once milk mixture has come to a simmer, lower heat. Temper hot milk into sugar-yolk mixture. Slowly add hot milk into sugar-yolk mixture about ¼ cup at a time, whisking to distribute heat. Once almost all the milk has been added to the yolk mixture, transfer everything back into the sauce pot.
Stir over medium-low heat until mixture reaches nappe consistency, or 180°F on a digital kitchen thermometer. Stir frequently to ensure mixture does not curdle or burn. Let mixture sit at 180°F for about 90 seconds to pasteurize eggs. Remove from heat and stir in salt.
Immersion blender: Place avocado in a large bowl. Pour about ½ of warm ice cream base into the bowl. Use immersion blender to puree mixture. Add another ½ of ice cream base until mixture is smooth. orBlender: Place avocados in a blender. Pour about ½ of warm ice cream base into blender. Place a towel over the top of blender to allow excess heat to escape. Blend. Add remaining half of ice cream base. Blend until smooth.
Transfer mixture to an airtight container and let mature in the fridge overnight.
The following day, freeze mixture in your ice cream maker according to your unit's instructions. Churn until the volume has increased by half and mixture has thickened to a soft serve consistency. Transfer ice cream to a freezer safe container and freeze for at least 1 hour to firm up.
Let ice cream sit at room temperature for 5 minutes to soften before scooping and serving.