In a medium bowl, whisk together almond flour, coconut flour, salt, and baking soda until well combined.
In a separate large bowl, mix the melted butter, brown sugar, and granulated sugar until smooth and creamy.
Add vanilla extract and milk to the butter and sugar mixture and stir until combined.
Gradually add the dry ingredients to the wet ingredients and mix until a dough forms.
Fold in the mini chocolate chips evenly throughout the dough.
Line an 8×8 inch square pan with parchment paper, leaving an overhang on the sides for easy removal.
Press the cookie dough evenly into the prepared pan, smoothing the top with a spatula.
Refrigerate the dough bars for at least 1 hour to firm up before slicing.
Once firm, lift the dough out of the pan using the parchment paper overhang and cut into 12 bars.
Store the bars in an airtight container in the refrigerator for up to 5 days.