1. Butter a baking sheet or line it with a Silpat (a French baking mat). Bring sugar and the water to a boil in a small, heavy saucepan, stirring until sugar dissolves; wash down sides of pan with a pastry brush dipped in water to prevent crystals from forming. Continue cooking, without stirring, until caramel is dark amber, swirling pan to color evenly. Remove from heat.

2. Immediately pour caramel onto prepared baking sheet. Let sit until hardened and completely cool; coarsely chop. Store in an airtight container at room temperature until ready to use, up to 1 day.