I took a gap year between my freshman and sophomore years of college. Let's just say I needed a break to find myself. One day I found myself on a bus between Mexico City and Campeche, a town on the Yucatán peninsula, and I was sitting next to an elderly Mexican woman. She didn't speak a word of English and I didn't speak a word of Spanish, but early in the morning as we were approaching some town between those two places, she offered me a cup of coffee from her Thermos.
The coffee was milky and sweet, and it was fragrant. Think café con leche with a cinnamon stick and an orange peel, left in a Thermos for several hours and opened only when the gray of the morning was pouring through the windows of a long-haul bus. —Hi, I'm Brian.
In a heavy non-reactive saucepan, stir together the cream, milk, milk powder, 1/4 cup sugar, coffee, cinnamon, chile de arbol, and the salt.
Put the pan over medium-high heat. When the mixture just begins to bubble around the edges, remove from the heat, cover the pan, and let steep for about 10 minutes.
In a medium heatproof bowl, whisk the yolks just to break them up, then whisk in the remaining sugar until smooth. Set aside.
Uncover the cream mixture and put the pan over medium-high heat. When the mixture approaches a bare simmer, reduce the heat to medium.
Carefully scoop out 1/2 cup of the hot cream mixture and, whisking the eggs constantly, add the cream to the bowl with the egg yolks. Repeat, adding another 1/2 cup of the hot cream to the bowl with the egg yolks. Using a heatproof rubber spatula, stir the cream in the saucepan as you slowly pour the egg-and-cream mixture from the bowl into the pan.
Cook the mixture carefully over medium heat, stirring constantly in a figure eight motion, until it is thickened, coats the back of the spatula or a wooden spoon, and holds a clear path when you run your finger across the spatula.
Strain the base through a fine-mesh strainer into a clean container. Set the container into an ice-water bath, wash your spatula, and stir occasionally until the base is cool. Remove from the ice-water bath, cover with plastic wrap, and refrigerate for at least 2 hours or overnight.
Freeze in your ice cream machine according to the manufacturer's instructions. While the ice cream is churning, put the container you'll use to store the ice cream into the freezer.