Shortening and butter combination is strongly recommended to help cookies maintain rise.
You can substitute the rum and brandy extracts with vanilla extract, and the nutmeg with cinnamon, if you prefer a more classic version of this recipe.
The amount of flour is critical in this recipe. I recommend measuring flour by weight (379 grams) instead of by volume.
I find that 10 minutes 30 seconds is the best amount of time for baking.