Combine the sugar and 1/4 cup water in a small heavy-based saucepan and bring to a boil over medium-high heat. Remove from the heat and let the sugar syrup cool. Stir in the amaretto.
Bring a large saucepan of water to a boil. Fill a large bowl with ice water. Using a small, sharp knife, cut a small X in the pointed end of each peach. Plunge the peaches into the boiling water for 1 minute. With a slotted spoon, remove the peaches from the water and put them into the bowl of ice water to stop the cooking. When the peaches are cool enough to handle, use a small sharp knife to gently peel the skin off the peaches, starting at the X. If the skins don’t peel off easily, return the peaches to the boiling water for another 30 to 60 seconds.
Halve the peaches lengthwise and remove the pits. Slice each half lengthwise into 1/2-inch-thick slices and put them in a medium bowl. Pour the amaretto sugar syrup over the peaches and stir gently to coat completely. Cover the bowl tightly with plastic wrap and let the peaches marinate in the refrigerator for at least 30 minutes and up to 2 hours before using.
Make Ahead Tips
You can make the syrup a couple of weeks ahead and refrigerate it, tightly covered. Don’t add the peaches too far ahead, though, as they will turn brown after a couple of hours in the marinade.
Instead of the amaretto, stir peach schnapps, Grand Marnier, Cointreau, or a dessert wine, such as Muscat (Moscato), Muscat Canelli, or Sauternes into the brown-sugar syrup
For deeper flavor, replace the light brown sugar with dark brown.
For lighter flavor, replace the light brown sugar with granulated.
Photo: Scott Phillips