Step 1: Prepare the Ice Cream Base

1. In a saucepan, combine heavy cream, milk, and sugar. Heat gently over medium heat until bubbles form around the edges. Remove from heat and let cool for 5 minutes.
2. In a bowl, whisk egg yolks and salt until pale. Slowly pour the warm milk mixture into the yolks while whisking constantly to temper them. Return to the saucepan.
3. Cook over low-medium heat, stirring constantly, until the mixture reaches 185°F (85°C). It should coat the back of a spoon without boiling. Stir for an additional 4 minutes at this temperature.

Step 2: Cool the Custard Base

1. Strain the custard through a fine mesh strainer into a bowl set over an ice bath. Stir occasionally until completely cool, then refrigerate for at least 2 hours or overnight.

Step 3: Make the Mocha Ripple

1. In a small saucepan, whisk together sugar, agave syrup, espresso, and cocoa powder over medium heat until bubbling. Reduce heat to low and cook for another minute until slightly thickened. Let cool completely before using.

Step 4: Churn and Assemble

1. Whisk Kahlua and rum into the chilled custard base. Pour into your pre-frozen Cuisinart ice cream maker and churn according to manufacturer instructions (~20–25 minutes). The texture should resemble soft serve when done.
2. Spoon half of the churned ice cream into a freezer-safe container. Drizzle half of the mocha ripple on top, then repeat with remaining ice cream and ripple. Use a knife to gently swirl without fully mixing. Cover and freeze for 4–6 hours until firm.