Make the cookies, according to the package with the egg, but instead of using a whole stick of butter, substitute half of the butter for sour cream.
While the cookies are baking, mix the crumb ingredients together with a fork.
Pull the cookies out of the oven 5 minutes early. Make a small indent in the cookie, pressing lightly in the center with the back of a lightly greased spoon. Press softly so that the spoon does not go through to the cookie sheet.
Fill the indent generously with some of the crumb mixture. Put the cookies back in for the rest of the time.
While they are baking for the last 5 minutes, make the glaze by mixing all the ingredients together until they are fulling combined and smooth.
Once the cookies are down, let them cool on the baking sheet for 10 minutes. Then drizzle over the brown sugar glaze. Let them cool for another 10 minutes.
Remove to a cooling rack.
You can eat them right away, but they are absolutely insane the next day...if you can wait that long.