Shortbreads, despite their three main components being butter, sugar and white flour, have proven to be one of the easiest things to make healthily. I substitute the butter with coconut oil, the sugar with coconut palm sugar or natural fruit sugars/syrups, and the white flour with buckwheat flour, oat flour, or nuts ground into a flour consistency. From there, it is easy to add other ingredients to increase the nutritional profile of your biscuits even more - such as superfood powders, raw vegetables and linseeds/flaxseeds or chia seeds. You can also very easily make these into savoury or sweet biscuits, simply reducing the amount of coconut palm sugar or syrup used for savoury biscuits (and adding vegetables, more flour and nutritional yeast for a cheesy flavour), or increasing the coconut palm sugar or syrup quantities to your personal taste, and adding things like low fructose dried fruit and super foods like maca and cacao. Once you've got the base down, you can add pretty much anything.
And you don't have to skip the icing either! Creamed coconut is a mysterious ingredient and, as it sets, resembles sugar icing almost exactly. I actually prefer it, as it has a nicer texture, a creamier flavour and doesn't leave a strange aftertaste or sugaring coating in your mouth after you've eaten it. While some of the colouring items are quite an investment, they're definitely worth it. I alternate adding each one to smoothies, porridge and soups as well.