However! I imagine (and will try it next time) that this can be made with 1 egg, instead of yolks. I will keep you posted.
Thumbprint Butter Cookies
From Gourmet, recipe can be halved
3 c rice flour mix
3/4 t xanthan gum
1 c sugar
1/2 t salt
3 sticks cold butter, cut into cubes
2 egg yolks
1-2 T milk (or juice)
jam of your choice (I used homemade peach marmalade)
Mix the rice flour, xanthan gum, sugar, and salt. Work in the butter until mixture is crumbly. Mix in the egg yolks, and if dough is too crumbly add a tiny bit of milk at a time, just until the dough holds together. Wrap tightly in plastic wrap and stick in the fridge for a few hours.
Preheat the oven to 350. Roll the cold dough into balls, press your finger into the middle to make an indent, and fill with jam. Bake 10-12 minutes, cool on cookie sheet. These can hang out, wrapped in plastic, for at least a few days on the counter.