I started by beating the eggs together, whole, as if you were making scrambled eggs. You could also blend them. For a 1 cup dose of coffee, I did two whole eggs. Once the eggs are beaten or blended, slowly drizzle in the coffee. You don’t want to cook the eggs. You want them to stay creamy. If you’re really concerned about the avidin in the raw white, dump the coffee in to ensure maximal heat exposure. Otherwise, just drizzle.
I think a higher egg:coffee ratio (using a large shot of espresso, for example) for a stronger coffee flavor would work really well. Also, two eggs in this recipe created a nice and creamy concoction. I suspect three eggs might even be better.
Again, I added a little sweetener plus some salt. It made the coffee taste a bit like a liquified custard. Really, really tasty.