Candi Sugar (Invert Sugar)

1 lb. (2 cups) sugar
1/2 cup water
1/8 tsp. cream of tartar

Mix all ingredients in a saucepan and heat slowly while stirring to fully dissolve the sugar.
Brush down the sides of pan with a wet pastry brush until there are no more sugar crystals.
Hold between 160°F and 235°F for 20 minutes, either using careful flame adjustment or a double boiler. Closely monitor the temperature throughout because the temperature will rise rapidly once the water has boiled off.
(optional) Raise temperature to 220°F and continue cooking, holding between 220°F and 235°F to caramelize sugar for darker color.
To make syrup: pour out and let cool.
To make rocks: heat to 300°F and pour into foil-lined baking sheet and let cool.