Melt 1 cup of butter together with 2 cinnamon sticks broken into small pieces, 1 vanilla bean-split and scraped, ¼ tsp freshly grated nutmeg. Simmer on medium heat until the butter turns brown and fragrant. Remove from heat and cover. Let steep for 15 minutes. Strain through a fine mesh sieve. Refrigerate 1 hour until it solidifies.
Blend together the spiced brown butter, regular butter and icing sugar until well combined.
Add in flour and mix until a smooth dough forms.
Form into a log and cover with plastic wrap and refrigerate at least 2 hours or up to 1 week.
Slice into ¼ inch pieces.
Bake at 350 degrees F 12-14 minutes, rotating sheets halfway through baking.
Let cool on baking sheet to firm up, then transfer to cooling rack to cool completely and then store in a tin up to 2 weeks.
Recipe by Chateau Elma at https://www.chateauelma.com/spiced-brown-butter-shortbread