Add the oats to a blender and blend until they form a flour-like consistency. Transfer the oat flour to a bowl and stir in the protein powder, cocoa powder, sweetener, and a pinch of salt until well combined. Add the Greek yogurt and milk, then stir until a thick but creamy batter forms. If the mixture is too thick, add a small drizzle of water to loosen it.

Divide the mixture evenly into small airtight containers and sprinkle each serving with chocolate chips. Refrigerate for at least 4 hours, or preferably overnight, before serving.