First, in a large bowl using an electric mixer, cream together the softened butter and brown and white sugars until lighter and fluffy. Add in the egg, egg white, and molasses/treacle and beat until smooth and lighter. Then mix in the gluten free flour, xanthan gum, cornstarch/cornflour, all spices, and baking soda and salt until combined. The dough will be thick and slightly sticky (if it's very sticky, add a bit more flour and mix). Scoop out dough into a small bowl and cover, then chill in the fridge for at least an hour (can be overnight).
Once dough is chilled, preheat oven to 350° Fahrenheit/180 Celcius and line two cookie sheets with parchment paper. Then, scoop teaspoons of the cookie dough and roll into 1-inch balls. Place balls 2-3 inches apart on cookie sheets (do not flatten cookies!). Bake for 11-12 minutes (do not overbake or cookies will be dry and crumbly). Let cool completely before eating or glazing.
These cookies are lovely on their own, but if you would like to add glazes, you can! If so: while cookies are cooling, make glazes. Use two cereal/every-day use bowls. In one, combine the ingredients for the ginger molasses glaze and stir vigorously with a small spoon until thick and smooth. You don't want the glaze too runny or it won't harden. In the other bowl, combine ingredients for the vanilla glaze and stir with spoon until smooth and combined.
Once cookies are cooled, glaze them (totally optional!). I put each glaze into a piping bag (without a piping tip) or a ziplock bag, and then snip off the very tip so that just a drizzle of glaze will come out. You can glaze the cookies however you want! Then enjoy!