Preheat oven to 350F. Grease and flour three 6 inch cake rounds and line the bottom of the pan with a piece of round parchment paper.
In a medium bowl, whisk flour, baking powder, and salt until well combined. Set aside.
Using a stand mixer fitted with a paddle attachment or a hand mixer, cream butter, earl grey tea and sugar on med-high until pale and fluffy - this usually takes 2-3 minutes. Reduce the speed of your mixer and add eggs one at a time fully incorporating after each addition. Add in your vanilla.
Turn off mixer and slowly add in your flour and milk to your creamed earl grey butter, fully incorporating the mixture before adding more.
Bake for 30 minutes or until a toothpick inserted into the center comes out mostly clean. If it's not clean, continue to bake in five minute increments, checking each time. I've never had to bake this cake longer than 35 minutes.
Place cakes on wire rack to cool for 10mins then turn out onto wire rack. Allow cakes to cool completely.
BUTTERCREAM:
Finely grind your lavender in a food processor or mortar and pestle.
Add the butter and one cup of the powdered sugar to the bowl of a standing mixer fitted with the whisk attachment. 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 heavy cream and another cup of powdered sugar. Beat on low speed to blend, then on high speed for another two minutes, stopping to scrape down the sides of the bowl a few times.
Add two more cups of powdered sugar and the salt and extract. Beat on low to combine, then on high for about 1 minute, until the buttercream is completely smooth.
Add in your honey and fine lavender.
Check the consistency and beat in more powdered sugar if the buttercream is too thin. Taste, and add more salt, vanilla if desired.