A fruit poaching syrup is typically the lightest of the syrups used in the pastry kitchen, at a ratio of 1 part sugar to 2 parts water by weight. Heavier syrups are sometimes used, certainly, but in general if you’re simply poaching peaches or pears, this is the formula you’d use:
8 ounces water
4 ounces sugar
1/2 teaspoon vanilla extract (or a little vanilla bean if you’re getting fancy)
2-3 lemon wedges
Combine all the ingredients in a saucepan and bring to a boil — done! Boil the fruit for five minutes, then lower the heat to a gentle simmer until the fruit is soft.
The nice thing about poaching syrups is that they can be strained and used again, either to poach fruit or as a light cake syrup.