Brew your espresso shots using your preferred espresso making method. Add lavender syrup to a cup, and add in the espresso.
Add oat milk to a milk frothing pitcher, and steam the milk using a steam wand on an espresso machine. If you don't have a steam wand, see the section mentioned above titled: How To Steam Milk At Home.
Pour the steamed milk over the lavender-espresso mixture, and enjoy!