Line two half sheet pans with silpats or parchment (see note). Set aside.
In a medium bowl, combine the dry ingredients (flour, espresso powder [see note], baking powder, and salt). Set aside.
In the bowl of a stand mixer, combine butter and sugar. Beat until light and fluffy (at least three minutes) Scrape down the sides of the bowl as necessary.
Add the egg and vanilla bean pate (see note) and mix to combine. Gradually add the dry ingredients, mixing until just incorporated.
Turn the dough out onto your work surface and divide in half, shaping each half into a disc about 1 inch thick. Wrap each disc and place in the refrigerator to chill for at least one hour.
Once chilled, working with one disc of dough at a time, roll the dough out to about ¼" thickness on a lightly floured surface.
Cut the dough into your desired shapes (I chose a 2.75-inch round cutter, see note). Place the cut-outs on the prepared baking sheets, and place in the freezer for at least 30 minutes before baking.
Preheat the oven to 350° F. Bake the cookies 8-10 minutes, turning the cookies around in the oven halfway through to help ensure even baking. Allow the cookies to cool on the pan for at least 10 minutes before removing to a wire rack to cool completely.
For Buttercream:
In the bowl of a stand mixer, beat the butter until smooth. Add the honey, lavender paste (see note), and salt. Mix to combine.
Gradually add the sifted powdered sugar and mix until incorporated. Add the milk and beat to combine. If the buttercream is too thick you can add a little more milk. If too thin, you can add a bit more powdered sugar until you reach the desired consistency.
Once the cookies are completely cool, frost with the buttercream. Sprinkle with dried lavender, if desired.
The cookie dough will keep, well wrapped, in the refrigerator for a few days, or for up to six months in the freezer. Once baked, they're good for about three days in an airtight container on your counter.For longer storage, bake them, cool them, and store in an airtight container in the freezer for up to six months! Just thaw the cookies in the refrigerator overnight, then frost them.Enjoy!
Notes
Note on silpats: I chose to line my baking pans with silpats because the cookies brown up a little slower and you can use them over and over again. If you prefer, you can line your pans with nonstick parchment. If you go with the parchment option, keep in mind that your cookies may brown up a little faster.Note on espresso powder: I've found it difficult to find espresso powder--especially one that isn't already hard as a rock--at my local grocery store. I use King Arthur Baking brand (link here), as it's very fine and made specifically for baked goods. Note on vanilla bean paste: It's no secret that I love vanilla bean paste. It's soooo tasty without the vanilla bean price tag (and it pretty much stays good forever). If you prefer to substitute, you can use an equal measure of vanilla extract.Note on cookie cutter: I used a 2.75″ biscuit cutter for my cookies. You can use whatever size/shape you like, just know that bigger cookies may take more time to bake, and smaller cookies less time.Note on lavender paste: Lavender paste is a convenient way to add lavender flavor without having to add actual lavender flowers to the buttercream. If you prefer to substitute, this is my suggestion: microwave the milk in a small bowl until warm, then add one teaspoon of lavender flowers and let them steep in the milk until it cools. Strain the lavender from the milk and use the lavender-scented milk in the buttercream as directed in the recipe. The flavor will likely be milder than if you had used the lavender paste.Note on lavender: You'll want to make sure that you're using culinary lavender, since other lavenders aren't meant to be eaten and could have been sprayed with harmful chemicals. I bought my lavender here.