Add the water and then the sugar to a small saucepan. Cook over medium heat until the sugar melts. Do not stir this mixture. If you feel that the sugar near the edges of the pan is not melting, use a butter knife to push the granules towards the center of the saucepan. If you see any sugar granules on the sides of the pan, use a wet pastry brush to wipe them away. Using a candy thermometer, simmer the mixture until thicken and it reaches 235 - 238ºF.
While the mixer is running on medium speed, slowly pour in the sugar syrup on the side of the mixing bowl. (Avoid the running beaters or it will only get on the sides of the bowl.) Once the syrup is all in, increase the speed to high and beat until thoroughly combined and the bowl is cool.
Add the flavoring of choice: extract, emulsion, jam, melted chocolate, berry puree, matcha powder, and more.
Use to fill a cake, cupcakes, French macaroons, and more.