In a medium bowl mix the flour and spekulatius spice mix together. Set aside.
In the bowl of a stand mixer with a paddle attachment or in a large bowl with a hand held beater beat the butter on high until light and fluffy, then add the brown sugar and beat again on high until light in colour, approximately 2 minutes. Add the egg and beat again on medium until thoroughly combined.
Add the flour/spice mix to the wet ingredients and mix on low until everything is combined. Cover the bowl or wrap the dough and chill for a minimum of 2 hours.
Preheat the oven to 350 degrees F and line two large baking sheets with parchment paper. Set aside. In a small bowl, whisk the egg for the egg wash and set aside.
Empty the dough onto a lightly floured work surface and roll it out to 1/4 inch thickness. Cut with cookie cutters and place 1 inch apart on the prepared baking sheets. Combine the dough scraps with your hands, then re-roll and cut until there is no or little dough remaining. Brush the tops of all the cookies with the egg wash and sprinkle the crushed sliced almonds on top. Bake for 12-13 minutes until the tops are shiny and the bottoms are golden brown.
Remove from the oven and allow to cool for 5 - 10 minutes before transferring to a wire cooling rack.
These cookies freeze really well!