This syrup is delicious over fruit or ice cream. It can also be used to sweeten hot or cold drinks.
Place almonds in a medium bowl and add 2 cups warm water. Let stand at room temperature for 2 hours. Transfer soaked almonds and water to a food processor and process until pureed, about 2 minutes.
Pour puree into a cheesecloth-lined sieve over a bowl and press hard to extract as much liquid as possible. Pour 2 more cups warm water over almonds and press again to squeeze out more liquid. Discard solids.
Pour almond milk through a fine sieve into a saucepan, add sugar, and stir to combine. Simmer over low heat until liquid reaches about 180 degrees on a candy thermometer, about 1 hour. Stir in almond extract.
Pour syrup into a clean 1-quart glass bottle or jar, let cool, and cover. Syrup will last, refrigerated, for up to 3 months.