Soften butter to room temperature.
Cream the butter and brown sugar in the mixer on high speed until smooth, lighter in color, and a little fluffy. If you don't have a mixer, you can do this by hand in a mixing bowl.
Add the 2 eggs, one at a time, beating well after each addition. Scrape down the sides of the bowl with a rubber spatula as needed.
Add the flour, pistachios, white chocolate chips, and rosemary. Mix on medium speed until thoroughly incorporated. The mixture should be solid, but a little sticky.
Line a baking sheet(s) with parchment paper.
Preheat the oven to 190°C (375°F).
Using a spoon or a fork, drop tablespoon-size (2.5cm/1") blobs of dough at least 5cm (2") apart onto a baking sheet(s).
Bake for10 minutes, until lightly browned at the edges and spread flat. Let cool on the pans.
Store in an airtight container at room temperature. They can also be stored in a freezer up to year.