Pour the heavy whipping cream and whole milk into a heavy saucepan, and place over a medium-low heat, and heat until barely simmering, stirring frequently. Turn the heat down to low.
Whisk together the egg yolks, sugar, and salt in a large bowl until thoroughly combined.
Slowly combine the hot cream mixture with the egg mixture, whisking constantly, a little at a time. When all is combined, return to medium-low heat, whisking constantly.
Add Expresso and chocolate syrup.
Stir until the mixture thickens and coats the back of a spoon. Do not let mixture boil.
Add Kahlua, and place mixture in refrigerator to chill overnight.
Freeze according to your freezers instructions.
Add chopped chocolate almonds and dark chocolate chunks towards the end of the freezing cycle, they just need to be stirred in.
Operating with a standard four-quart home ice cream machine requires strict adherence to thermal limits when building a dairy base. Standard countertop compressor units cannot rapidly cool boiling liquids, making the chilling stage mandatory.
The Custard Base
Whisking eight egg yolks with three-quarters of a cup of white sugar denatures the proteins, preventing curdling when the hot liquid enters. Heat the whole milk and heavy whipping cream on medium-low until the surface shimmers at a gentle simmer, just under 180 degrees Fahrenheit. Tempering the eggs by streaming the hot dairy slowly while whisking constantly prevents scrambling. Cook the combined mixture until it coats the back of a spoon cleanly, typically reaching 170 degrees Fahrenheit, and immediately remove the pan from the direct heat source.
Chilling and Alcohol Addition
Incorporating two tablespoons of Kahlua lowers the freezing point of the liquid due to the ethanol content. This chemical adjustment keeps the frozen dessert scoopable straight from a zero-degree freezer without forming rock-hard ice crystals. Place the saucepan contents into the refrigerator for a minimum of eight hours. Liquid temperature must drop below 40 degrees Fahrenheit before churning begins, otherwise the dasher will fail to incorporate air.
Mix-In Integration
Adding three-quarters of a cup of chopped chocolate-covered almonds and eight ounces of dark chocolate too early causes the solids to sink to the bottom of the canister. Introduce solid mix-ins during the final two minutes of the churn cycle. This mechanical delay ensures even distribution throughout the dairy matrix.