Preheat your oven to 375°F and line a sheet pan with parchment paper.
Mix the ground flax seed and water, and let it sit for 5-10 minutes to thicken.
In a mixing bowl, combine melted butter and both sugars. Use an electric mixer on medium speed for 2 minutes. Add the flax “egg” and vanilla, and mix until well combined.
Add in the flour, salt, and baking soda. Mix until the dough comes together. Fold in both types of chocolate.
Use a cookie scoop (a large 3 tbsp scoop works well) to portion the dough. Place the scoops 1 inch apart on the baking sheet. Optional: sprinkle some flaky salt on top.
Bake for 10-11 minutes. Once done, remove from the oven and let them cool for 10 minutes before indulging in these delightful treats. Enjoy!