As its name suggests, this is easy. It's also useful as a technique for steeping different flavors into sugar water for various uses, such as moistening cake layers. Simply syrup is very helpful brushed on layers of genoise before icing.
Place the sugar, water and mint into a pan large enough to hold it. Bring the ingredients to a boil, remove from heat, cover and allow to steep 20 minutes.
Strain the syrup, pressing on the mint to release as much extra flavor as possible.
Store in a resealable jar in the refrigerator.
There are many ways to enhance a simply syrup. At its simplest, it is only the sugar and water. The mint is infused as a tea would be. You may change or add thyme to that, lemon zest, lavender, honey as part of the sugar.
Depending on the use of the syrup, you can make any flavor you wish.