Coffee flavored melted chocolate for drizzling over cookies?
If you can get instant espresso powder (most big grocery stores in the US have it) that's what you want to use. NO WATER, small amounts of water will ruin chocolate, cause it to seize.



Just sprinkle some powder in while the chocolate is melting. It will blend right in.

If you can't get espresso powder, you can use instant coffee, just be sure that it's a fine powder, or powder it yourself in a spice or coffee grinder.

To be sure that the instant coffee is fine enough, you might consider sifting it. Either powdered regular instant coffee or even the instant espresso might benefit from that.