I am trying macarons once again so I have a lot of yolks hanging around. Can I use just the yolks in a sugar cookie recipe? Would it bake differently? What should the substitution be? Two yolks = 1 whole egg?
It's really tricky to make a direct substitution like this. The yolks have a fair bit of fat, in addition to protein, in them, so they tend to have a tenderizing effect on doughs. Whereas the whites have no fat whatsoever, and lots of protein, so they have a strengthening effect. Why not save the yolks for creme anglaise or pastry cream or something else, which only call for yolks?
Adding a suggestion for egg yolk uses (I also think perhaps cookie dough could react oddly to just yolks if they are ones for decorating, I did once see a recipe for snickerdoodles which just used yolks though, though my brain being what it is I cannot remember where - sorry)
Lemon curd is one I tend to make with lots of leftover egg yolks, it keeps really well in a sterilised jar and makes a nice filling for sandwich cookies, cupcakes (I also use it drizzled on top), cakes and cheesecakes.
Hollandaise souce I use it on ham rolls filled with brócoli and cheese, but you can use on many other meats. There are many récipes if you look for egg yolks récipes on internet.
Thanks for the responses. I think I will give the lemon curd a try.
You can always throw an extra egg yolk or two into a meatloaf. You can freeze them, too.
But I would agree with Julia that using only yolks in your sugar cookie dough would likely cause an extra soft crumb to your final product. I think you need the protein strands of the egg white to add structure for roll-out cookies--or else they might not retain their shapes and sharp edges when you bake them.
Edited to add: You would do better to leave out the egg entirely than to add yolks without their whites. Some sugar cookie/shortbread recipes don't call for any eggs at all.
The lemon curd is awesome but the macarons are still a work in progress. First time around they were too flat, this time they were too poofy. Maybe next time they will be just right. I am using "Ultimate Cookies" Goof-proof Macaron recipe and everyone says the flavor is excellent. Thanks, Julia!
A desert alternative:
My mother in law had this Caramel Pie, my husband's fav' and I always wait until I have egg yolks to do it.
1 pie shell OR you could just make caramel and top with whipped cream..
-1cup of brown sugar +
-3 tbls flour
-1cup of milk
Cook in double boiler or heavy sauce pan.
*Mix brown sugar with flour
*Beat milk with yolks
*Add to sugar/flour
Cook mixture at low temp. stirring constantly and add *Butter at the end
Caramel is ready when thickened enough to pour in pie shell
Best topped with Whipped cream.
Note: Long to stir, but well worth it.