I brought them to work, for a co-worker's birthday. They were generally acclaimed.
They're simple to make, but do require a food processor. I made them in two single-pan batches. Baking two pans at the same time at different levels in the oven is just asking for trouble.
Do what the recipe says. Do NOT over-process or over-beat or over-cook. If you process the nut/sugar mixture much, or over-beat the flour/shortening (you are cutting the shortening into the flour), you will wind up with a greasy mess. You can still bake it, and it will taste okay, but it will have a different texture, and the bits of dough will be harder to handle.
Watch the cookies closely while they are in the oven. Remove them when the edges are slightly brown. If you let them get even a little too brown, the taste suffers.
I want to try them with pecans instead of almonds. Or walnuts. Or even macadamias. A touch of cinnamon might also be interesting. Maybe a little lemon zest?
Vanilla would be tricky. Even a trace of liquid will change the physical properties of the dough, and the finished cookie, perhaps drastically. Vanilla in the form of vanilla bean ground to a dust might be an option.