In a large mixing bowl, whisk together the melted butter, sugars, tahini, non-dairy milk, and vanilla extract until well combined. Add the flour, salt, and baking soda. Use a rubber spatula or wooden spoon to combine the dry ingredients into the wet until almost no flour remains. Fold in the chopped chocolate until well distributed and no visible flour remains. Cover bowl and refrigerate for at least 30 minutes (or overnight).

Preheat the oven to 350°F. Line a large baking sheet with parchment paper. Use a large cookie scoop (#12 scoop, ~5 tbsp) to distribute dough onto baking sheet. Bake for 10 minutes. Remove from oven and tap the baking sheet against a flat surface a few times to create wrinkles. Bake for an additional minute. Allow cookies to cool on baking sheet for 5 minutes before transferring to a wire cooling rack. Sprinkle over flaky sea salt and enjoy!