Have ready a buttered or sprayed 8-inch square pan lined with parchment paper.
Heat ¾ cup peanut butter and 6 tablespoons unsalted butter until soft to mix them. I use the microwave and a large mixing bowl. If you use a small container, transfer the mixture to a large bowl.
Stir in ¾ cup traditional oats, pinch salt, 1 cup ground plain chocolate cookies, ⅔ cup confectioners sugar and 3 ounces semisweet chocolate , finely chopped, to the peanut butter mixture.
Mix well with a silicon or rubber spatula or a wooden spoon until no dry parts remain. It might take a few minutes. The dough will be shiny and dark.
Put it in the prepared pan, covering it as even and as smooth as possible. You might aid yourself with the back of a spoon that is lightly dipped in water.
Refrigerate for several hours until it solidifies, and the oats absorb liquid and become chewier.
When you’re ready to cut the bars, take the whole thing from the pan and transfer it to a board.
In a bowl heat 3 tablespoons cream with 3 ounces semisweet chocolate until melted and smooth. I do it in the microwave in 10-second spurts, whisking well each time and making sure I don't scorch the chocolate.
Pour it over the bars. You can spread it with a spatula or use a piping bag or fork to make a pattern.
Sprinkle some confetti over it, if desired, before the chocolate settles.
Keep leftovers refrigerated and well wrapped.