For the base: In a small saucepan, combine the milk, heavy cream, honey, lavender, and salt over medium heat and bring to a gentle simmer, stirring occasionally.
Meanwhile, in a medium bowl, whisk the egg yolks until smooth. Slowly add 1 cup of the warm liquid, whisking constantly to avoid cooking the egg. Add this mixture back to the saucepan with the remaining cream mixture. Cook over medium heat, stirring constantly with a rubber spatula, until the mixture is thick enough to coat the back of a spoon, 3 to 4 minutes. Remove from the heat and pour through a fine-mesh strainer into a clean bowl. Place a piece of plastic wrap directly on the surface of the ice cream base and chill completely in the refrigerator, at least 4 hours but ideally overnight.
Freeze the base according to your ice cream maker's directions.
To serve: Spoon the ice cream into bowls and drizzle with the honey. Garnish with chopped macadamia nuts.