Preheat the oven to 350F and add the butter to a 9x13 glass or ceramic baking dish. Place the dish in the oven as it preheats, to melt the butter.
In a medium bowl, whisk together the almond flour, sweetener, protein powder, cocoa powder, baking powder, and salt. Break up any clumps with a fork.
Once the butter is melted, remove the pan from the oven. Sprinkle the dry ingredients over the melted butter as evenly as possible.
In another bowl, whisk together the cream, water or coffee, and vanilla extract. Whisk in the collagen peptides. Drizzle this mixture over the dry ingredients as evenly as possible.
Bake 20 to 25 minutes, until the cake is mostly set. Remove and sprinkle with the chocolate chips. Let cool 10 minutes before serving warm.