If an espresso-roast coffee bean is too strong for your taste, substitute a Viennese, French, or any dark-roast bean.
Place espresso beans on a cutting board, and gently crush them using a heavy saucepan or a hammer (be careful not to pulverize the beans). In a medium saucepan, heat milk and coffee beans. Bring to a gentle boil, cover, and remove from heat. Allow to steep for 30 minutes. Strain mixture, and reserve milk; discard solids.
Combine egg yolks and sugar in the bowl of an electric mixer. Beat at medium-high speed until very thick and pale yellow, 3 to 5 minutes. Meanwhile, return milk to heat, and bring to a simmer.
Add half the milk to egg-yolk mixture, and whisk until blended. Stir into remaining milk, and cook over low heat, stirring constantly, until mixture has thickened enough to coat the back of a spoon.
Remove from heat, and immediately stir in cream. Pass mixture through a strainer into a medium mixing bowl set in an ice bath until chilled, stirring from time to time. Stir in instant espresso, then freeze in an ice-cream maker according to manufacturer's instructions.
For best flavor, soften gelato slightly in the refrigerator before serving.