Place milk and cream in a heavy-bottomed pan on the stove and heat on medium until the mixture just begins to steam. While milk is heating, whisk egg yolks with sugar, salt, and corn starch until just light and fluffy.
When the milk is ready, slowly ladle some milk into egg yolks to temper them (which means bringing them to the warm temperature without cooking them). After a few ladles, add eggs back to milk and set back on the stove. Stir over medium-high heat until mixture thickens and coats the back of a spoon, about 6-8 minutes.
Strain through a fine-mesh strainer and chill for at least eight hours. Freeze in ice cream freezer according to manufacturer’s instructions.
To assemble each affogato, add 2-3 scoops of the gelato to a glass. Pour in a splash of amaretto and a shot of espresso. Serve immediately.