One of them looks like this..
She started it, but I had to do the baking. Last weekend she came home from a long hard shopping trip with a real shortbread tin. The sort with patterns and cut lines molded in it. Sorry, no pictures.. it's in the dishwasher right now.
After several experiments, I iterated towards the following recipe, which is as good as I've got so far. When squished in the shortbread tin and cooked, they look something like this..
Better Shortbread Recipe
Shortbread is supposed to be 'short', meaning tender and crumbly, the opposite of bread which is chewy and robust. To do this you need to minimize the development of gluten, the opposite of what you do to bread.
Things you can do to prevent gluten development are to keep it cold (as with pastry), avoid kneading it (as with pastry) and use soft flour (as with pastry). Another thing to improve lightness and crumbliness is to get air into the mixture by creaming the sugar and butter. Cutting the butter with the flour rather than folding/kneading it in is also good, since the butter is incorporated as little butter particles, rather than being uniform, so when it melts it leaves zones of high and low density, adding to crumbliness.
These things are at odds, because to cream butter, it has to be warm enough to be creamed. So you can't then cut it in because the butter is softened.
So my solution (as with bread) is to take the extra time to make it right. Namely cream the softened butter, sugar, salt and any flavoring vigorously in a mixer to get it well airated, then wrap it in wax paper or parchment (silicone paper) and stick it in the fridge for a few hours or overnight to re-harden.
Then cut the hardened butter/sugar mixture into the flour with a pastry cutter and cook. Keep your tools, flour and bowls cool, so it's good to stick them in the fridge with the butter while it hardens.
The shortbread needs to be cooked low and slow to prevent it browning, while giving it enough time to cook through.
Also a nice thick shortbread will spread out in the oven as the high butter content melts. So instead of baking it on a cookie sheet, bake it in a cake pan, lined with parchment so you can get it back out again. I used a Williams & Sonoma Goldtouch nonstick 9" round cake pan. The gold colour seems to strike the right balance between heat absorption and reflection. My black cake tins are good at burning things. If wifey/hubby brings home a proper shortbread pan, use that.
One sign of success with this recipe is that the baked dough rises up a little and so the top undulates a bit. This is evidence that air was incorporated during the creaming.
My experimentation led me to a good ratio of sugar:butter:flour of 1:2:2.25 by weight.
I found that adding vanilla is a good thing, filling out the flavour a bit.
For consistency, use unsalted butter, so you can control the amount of salt and measure all the bulk goods by weight, not volume.
While the recipe below is a single batch recipe, it's handy just to make up larger batches of sugar/butter mix ahead of time and then weigh out as much as is required to fill whatever vessel you are cooking it in.
--- Day 1.
4 oz powdered/icing sugar
8 oz (two US sticks) of room temperature unsalted butter. (remember to take the butter out a few hours earlier)
1 teaspoon vanilla extract
1/2 teaspoon salt
9 oz cake flour
Cream the sugar & butter in a stand mixer with a scraper blade. Start slow to keep the power under control. Once it is coming together run it for a few seconds at a faster speed then stop.
Add the vanilla and salt then mix at a fast speed for a couple of minutes to airate the mixture.
Use a spatula to scrape all the butter onto the middle of a large sheet of wax paper (parchment will work, but sellotape doesn't stick so well) roll it into a log in the paper, twist the ends to tighten it and tape it shut. Put this in the fridge overnight or for several hours, to cool, along with the flour and bowl you will be using later.
--- Next day
Put the cold butter/sugar mix into the flour and cut it in with a pastry cutter. Then use your fingertips, like as with pastry, to rub it together to form breadcrumbs, while avoiding warming it up too much. Unlike pastry, following the breadcrumbs, it will start coming together as a dough. This is the time to scrunch it together to form a dough ball, flatten to a disk, wrap in pastic wrap and put in the fridge for 15 minutes to relax it, so it'll shape more easily.
If it remains to crumbly to form a dough, wet your hand and shake a few drops of water in the bowl, then mix in with a knife. This should get it to come together.
Prepare a 9" straight sided round cake pan, putting parchment in the bottom and greasing the sides with butter or Pam. Or grease the shortbread pan wifey brought home.
Press the dough into the bottom of the pan, get it to reach the sides, then use a flat object, like the bottom of a glass to press the surface reasonably flat.
If you're cooking it top-up, poke the top all over with a fork (mostly for traditional decoration) and pre-cut the segments with a sharp knife, so they can be broken apart after cooking. Sprinkle with sugar and/or turbinado sugar.
If you're cooking in a shortbread mold, the top is down, so you can't really sprinkle things on it.
Cook in a pre-headed 275F oven for 1 hour. Take out and decant onto a cooling rack, cut it into separate parts, move them apart a little bit and return on the rack to the oven for another 30 minutes. This gives them a lot more open surface area, so it gets them to dry out properly.
Take out and allow cool and harden completely.
The result should be crumbly, sweet, melt in the mouth, reasonably dry and short (not chewy).