Preheat the oven to 350°F (175°C). Line an 8 x 4 inch loaf pan with parchment paper, leaving some overhang for easy removal later.
In a medium bowl, whisk together the honey and the egg whites until smooth and fully combined.
Add the pistachio flour and fold with a spatula until the pistachio flour is fully and evenly incorporated. Transfer the batter to your prepared loaf pan.
Bake for about 20-25 minutes or until the surface is set and lightly browned around the edges.
Allow the bars to cool fully in the pan before removing and cutting them with a sharp knife.
If desired, you can dust the bars with powdered sugar and chopped pistachios before serving.
Store uneaten bars in an airtight container in the fridge or freezer.
