Mix the cocoa with 1 cup of the half-and-half in a medium saucepan over medium heat, whisking to combine. Add the remaining half-and-half and the heavy cream. Bring the mixture just to a simmer, stirring occasionally, and remove from the heat.

In a medium bowl, whisk the egg yolks until they lighten in color. While whisking, slowly add the sugar until it has all been added and combined. Temper the cream mixture into the eggs and sugar by gradually adding small amounts (I use the 1/2 C used to measure the cocoa) and whisking constantly, until about 1/3 of the cream mixture has been added. Pour in the remainder and return the entire mixture to the saucepan and place over low heat. Continue to cook, stirring frequently, until the mixture thickens slightly and coats the back of a spoon or reaches 170 to 175º F. Pour the mixture into a container and allow to sit at room temperature for 30 minutes. Stir in the vanilla extract. Place the mixture into the refrigerator and once it is cool enough not to form condensation on the lid, cover and store for 4 to 8 hours or until the temperature reaches 40º F or below. (I've never waited that long . . . )

While the mixture is cooling, toast your almonds. Preheat oven to 325ºF. Spread the almonds out on a rimmed baking sheet. Cut the tablespoon of butter into a few pieces and scatter over the almonds. Put the almonds in the oven. Check and stir them every couple of minutes. The almonds can burn quickly so don't neglect them! Once you've reached a satisfied level of toastiness, remove from oven and allow to cool. Once cool, chop and set aside.

Pour the mixture into an ice cream maker and process according to the manufacturer's directions. When the ice cream is almost done, add the almonds to the ice cream maker. Serve as is for soft serve or freeze another 3 to 4 hours to allow the ice cream to harden.