Preheat oven to 350 degrees and line a 12 cup muffin pan with cupcake liners.
Process lavender to turn it into a fine consistency. You can do this in a food processor, in a spice grinder, or with your mortar and pestle. This step is optional, but will ensure you have a more even texture throughout your cupcakes.*
In medium bowl combine flour, baking powder and salt. Set aside.
In small bowl mix together wet ingredients: buttermilk, honey and vanilla. Set aside.
In a large bowl beat butter, lavender and sugar on medium - high speed until combined. You can use a hand mixer or make in the bowl of an electric mixer / stand mixer fitted with the paddle attachment.
Add eggs, one at a time, beating well after each addition and scraping down sides of bowl as needed.
Gradually add the dry and wet ingredients, alternating starting and ending with dry ingredients and mix until combined.
Using ice cream scoop fill cupcake liners about ⅔ full. Simply spoon batter if you don't have an ice cream scoop.
Bake for 18-20 minutes, until toothpick inserted into cupcake comes out clean. Make your buttercream while they bake.
Let cupcakes cool in pans for 5 minutes, then remove cool cupcakes to wire rack to finish cooling.
Let cupcakes cool completely before adding buttercream.

Finely grind your lavender the same way as you did for your cupcakes.
Add the butter and fine lavender and one cup of the powdered sugar to the bowl of a standing mixer fitted with the whisk attachment or a large bowl if you're using a hand mixer.

Beat on low just to blend, then beat on high for 3 minutes, stopping to scrape down the sides of the bowl a few times.

Add the honey, heavy cream and the remaining powdered sugar, mix until completely smooth.

Check the consistency and beat in more powdered sugar if the buttercream is too thin. Taste, and add more salt, vanilla if desired.

Move buttercream to a piping bag and pipe onto cooled cupcakes with any piping tip of choice