For the lilac sugar

Cup of Yum
1. To make the lilac sugar, add the sugar and the lilac blossoms to the bowl of a food processor and pulse until combined. The sugar should take on a pale lilac hue. This makes about 1 cup of sugar, in order to fit the bowl of a standard food processor, but you will only need 1/2 cup for the shortbread recipe. (you can make just 1/2 cup of sugar in a small capacity food processor, if you have one)

For the shortbread cookies

1. Preheat oven to 350F.
2. Add the flour, butter, 1/2 cup of the lilac sugar, salt, and vanilla extract to the bowl of a food processor. Pulse to combine, continuing until the dough comes together into a single clump.
3. Remove the dough from the food processor to a lightly floured surface, and roll out the dough into a rectangle. Scatter about half of the whole lilac blossoms over the dough, and then fold the dough a couple times to work them in, and re-roll it out into a rough rectangle. I like to divide my dough in half and do this twice.
4. Scatter the remaining lilac blossoms over the dough, and roll the dough out until it is about 1/4-1/3 inch thick, making sure the lilac blossoms are well embedded into the dough. Use your fingers to gently press them in, if needed.
5. Using a 2 inch biscuit cutter, or other circular cutter, cut out about 24 cookies and place them on a baking sheet.
6. Bake the cookies for about 15 minutes or until just barely starting to turn golden on the edges. Remove and allow to cool on the baking sheet for a few minutes before moving.