Loukoumi Chiou (Chios Mastic Loukoumi)

Instructions

1. Line the pan with parchment, brush with the sunflower oil, and dust with 10 g of the finishing cornstarch.
2. Bring the 800 g sugar, 250 ml water and lemon juice to a boil in a heavy saucepan, stirring until dissolved. Boil without stirring until a candy thermometer reads 240°F (115°C), 15 to 20 minutes. Keep it hot.
3. Meanwhile whisk the 110 g cornstarch, cream of tartar and 800 ml cold water in a large heavy pot until smooth. Cook over medium heat, whisking constantly, until it turns into a thick, glossy, gluey paste, 5 to 8 minutes.
4. Pour the hot syrup into the starch paste a little at a time, whisking hard after each addition until smooth.
5. Lower the heat so the mixture barely bubbles and cook, stirring with a heatproof spatula every 5 minutes and scraping the bottom, until it turns pale golden and very thick, about 60 to 75 minutes. It is ready when it reads about 235°F (113°C) and a dab dropped into cold water forms a firm, springy ball that does not stick.
6. In the last 10 minutes of cooking, grind the mastic tears with the 5 g sugar in a mortar to a fine powder and sprinkle it over the mixture a little at a time, stirring hard so it melts in evenly.
7. Pour into the prepared pan and smooth the top with an oiled spatula. Leave uncovered at room temperature until set and firm, at least 12 hours.
8. Mix the powdered sugar with the remaining 30 g cornstarch and sift some over a board. Turn the slab out onto it, peel off the parchment, and cut into 1-inch (2.5 cm) cubes with an oiled knife. Toss the cubes in the sugar mixture.