How easy is this?
All you need is equal parts fully opened lilac blossoms, green stems removed, and granulated sugar.
Blend in a food processor till the blossoms have completely broken down. The finished sugar will be moist due to the moisture content of the fresh blossoms, so lay out the sugar on a parchment lined baking sheet and let them air dry.
You can speed up the process by heating the oven to 200 F, placing the baking sheet on the center rack, and then turning off the heat. In no time the sugar will be dried out. It will be a tad clumpy, so just give it another whiz in the food processor. Or you can just do so by hand using a mortar and pestle.
Et voila, the most fragrant sugar you will ever come across! Even as it was drying out in the oven, the kitchen was already taking on a lovely perfume. I had enough for my pie, as well as for tea for the next little while! I also added a few crushed lilac petals to the ground sugar, just for color and added texture.
From: Food 52