If using culinary lavender buds, a day ahead of time, infuse the lavender into the sugar as follows: combine the two in a sealed container and let sit overnight for the sugar to pick up the lavender flavor.
On baking day, preheat oven to 325 F. Cream the butter and lavender sugar mixture or the butter, sugar and lavender paste. Add the lemon zest.
Blend the cornstarch and flour together and add to the butter mixture a little at a time. The mixture is thick, so I finish mixing by hand.
Knead the dough a couple times to finish mixing, then roll out on a floured surface to 1/8 – ¼ inch thick. Cut with a round cutter.
Bake at 325 F for 10-15 minutes until set with just a hint of browning.
Let cookies cool completely before icing them. Or if you'd like you can stop here and eat them undecorated!
To make and apply the royal icing:
Using a mixer at low to medium speed, beat together powdered sugar, meringue powder, 4 Tablespoons water and vanilla, until smooth and fluffy. Don’t beat at too high a speed or you’ll risk incorporating a lot of larger air bubbles.
You will want to achieve a thinner consistency that can be dipped into but not so thin it doesn’t dry. If the icing is too thick, stir in more water a teaspoon at a time, by hand. If the icing is too thin, add a little more sugar.
Let the icing sit for 15-30 minutes for bubbles to escape. You can tap the bowl on the counter to assist in this.
Dip each cookie top in the royal, letting excess drip off, and turning to catch final drips (the drip will level when you set the cookie down). Set cookies on plate or rack to dry. If there are some air bubbles, you can prick with a tooth pick to remove (some may disappear too). Let sit until completely dry, at least a couple hours but ideally overnight. Drying time will vary based on the wetness of the icing.
To apply stencil:
In a small dish or bowl, put a few drops of a liquid (I used lemon extract) and a little luster dust. Using a brush like on a palate, mix a little of each together into a thin mixture without clumps.
Hold the stencil on top of the icing as flat as possible. Dab the stencil openings with the luster dust mixture until your desired color is achieved. Remove stencil and set the cookie aside to dry.
I am not a health professional and nutrition data is calculated programatically. Accuracy may vary with product selection, calculator accuracy, etc. Consult a professional for the best information.