Brown the butter in a small saucepan. Turn off the heat when the butter smells very nutty and the milk solids have browned. Set aside the pan to cool slightly.
In a large bowl, whisk together the granulated sugar with the chestnut flour and the ground almond.
In a separate medium bowl, beat the egg whites with the salt until they are frothy and quite thick.
Pour the egg whites over the dry ingredients and whisk them in, then add the vanilla and the browned butter and stir to incorporate everything together really well.
Wrap the bowl in plastic wrap and chill 30 minutes.
Preheat the oven to 350ºF. Butter 16 wells of a mini-muffin pan and flour them with sorghum flour, tapping out the excess. Make sure that the sides and bottoms of the muffin wells are evenly coated.
Divide the batter between the 16 wells of the pan, and top with 2 to 3 frozen cranberries, pressing them down slightly.
Bake for about 25 minutes until the edges begin to brown.
Let cool 5 to 10 minutes so that the financiers firm up before unmolding them onto a wire rack to cool completely.