In a large bowl add the almond butter and maple syrup and mix to combine. Then add the protein powder, oat flour, milk, vanilla extract and cinnamon. Mix to combine, the mixture will be thick.Pour into small pan or dish and use hands to press down. Using spray or parchment paper will help the bars from sticking to the pan. Freeze for 30 minutes.In a small bowl, add the dark chocolate and coconut oil and microwave for 30 second intervals until melted. Pour over the bars and use a spatula to spread evenly. Add sea salt if desired. Freeze again for 10 minutes.Cut into 12 bars, and store in the refrigerator or freezer.