1) Preheat the oven to 325°F. Prepare your shortbread mold according to the manufacturer's directions by very lightly greasing and flouring the mold. Or lightly grease two 8" round cake pans.
2) Beat the butter until smooth.
3) Beat in the sugar, salt, and whiskey or vanilla until fluffy.
4) Mix in the flour and rice flour.
5) Divide the dough in half; each half will weigh about 11 ounces. Wrap and chill for 1 hour.
6) Press half the dough into the shortbread mold (or half into each of the 8" cake pans).
7) Prick the dough all over with a fork to prevent it from puffing.
8) Bake until the shortbread is golden, 32 to 38 minutes. Check at 18 minutes; if shortbread's puffing up; use a flat spatula to press the dough down into the mold. Continue to bake until golden.
9) Remove from the oven, cool for 15 minutes, then loosen the edges of the shortbread with a table knife before turning the mold over onto a flat surface.
10) Tap the bottom of the mold several times until the shortbread comes out.
11) Cut each round into 8 wedges using a serrated knife.
12) Store shortbread, well wrapped, for up to a week; freeze for longer storage.