Cookies – How to substitute English Toffee in cookies

Three things:

-You can flavor the sugar by mixing aromatic herbs into it and leaving it sit for a week or two. Rosemary pairs well with sweet desserts, as would lavender or basil. Sift out the herbs once you're ready to use the sugar.

-You can try replacing the butter in this recipe (or half of it) with some very good olive oil, as in this recipe from the NYT:

http://dinersjournal.blogs.nytimes.com/2008/03/07/recipe-of-the-day-olive-oil-cookies-with-red-wine-and-rosemary/

That recipe isn't for shortbread cookies, but the technique may still be valid. No guarantees that it will give you the texture you want, but great olive oil has all of the grassy and fruity characteristics that you're after.

-I'm not terribly familiar with matcha, but couldn't you just take some regular green tea leaves and powderize them in a spice grinder?

Since those are drop cookies, the best approach is to portion them into individual cookie portions, and freeze them on a sheet tray. Once solidly frozen, they can be moved into a zip back or other more convenient storage container.

They do not need to be thawed in order to bake, so they still are very convenient. Simply lay them out frozen on a tray, and bake.

It will take a minute or two longer than the regular non-frozen time. It might be helpful to drop the temperature by 25 F or so, but it shouldn't really be necessary.

The real issue with holding the dough is not just food safety (you should get 2-3 days given raw eggs as the most perishable ingredient); this doesn't give you a very large window. Eat By Date suggests 3-5 days.

It is also the loss of leavening power as the baking powder may slowly react, although the dough should be thick enough that most gets retained.