Preheat the oven to 375 degrees F. Butter the bottom of an 8-inch baking dish and set aside.
Using a melon baller, clean out the red flesh from the center of each peach. Arrange the peaches cut side up in the prepared dish. In the bowl of a food processor, add the amaretti cookies and pulse until finely crumbled. Divide the amaretti crumbs between the peaches. Fill the center of each peach with the amaretti cookie crumbs. Sprinkle 1/2 teaspoon of sugar over each. Dot each peach with 1/2 teaspoon of butter.
Bake until the peaches are tender and the filling is crisp on top, about 30 minutes. Serve warm with whipped cream.