Place the amaretti in a ziplock bag and crush them using a rolling pin.
Halve the peaches and remove the pits. Lightly carve the inside of the peaches to remove a little pulp, leaving edges that are all the same thickness (about a half cm). Place the peaches in an oven dish.
Combine the carved peach pulp with the sugar, egg yolks and cocoa and mix with a fork to create a homogeneous paste.
Add the crushed amaretti to the mixture and stir in.
Divide amaretti mixture between halved peaches.
Add a thin slice of butter over the top of each stuffed peach.
Bake in the preheated oven at 200°C (390°F) for 15 minutes, or until the peaches feel soft and cooked through.
Notes
Serve either hot or cold. Amaretti stuffed peaches taste best lightly warm. They microwave well.