Just because you're missing half the ingredients doesn't mean you shouldn't make cookies.
1. If you run out of baking powder, mix baking soda with cream of tartar.
2. Mix white sugar and molasses to make brown sugar.
3. You can substitute regular milk + lemon juice or vinegar for buttermilk.
4. Finely grind regular sugar with cornstarch to make confectioner's sugar.
5. Replace baking chocolate with a mix of cocoa powder and butter or shortening.
6. "Pumpkin pie spice" is just a mix of 5 common spices you probably have already.
7. If you have milk and sugar, you can make your own sweetened condensed milk.
8. All you need to DIY almond flour is slivered almonds and a blender or food processor.
9. A good blender can also turn popcorn kernels into cornmeal.
10. DIY peanut butter chips just take 4 ingredients to make.
This is a little bit more of a rainy day project than a last-minute swap, but it's so cool. And it's nice to have chips that you know aren't full of weird chemicals. Get the recipe at Minimalist Baker.
11. Make your own cake flour by sifting all-purpose flour with corn starch.
Joy Wilson / joythebaker.com
Replacing some of the all-purpose with corn starch mimics the lower protein content of cake flour, which is perfect for making finely textured, fluffy baked goods. Get the instructions here.
12. Replace corn syrup with homemade cane sugar syrup.
Emma Christensen / thekitchn.com
Corn syrup is useful because it's an "invert sugar" that keeps sweets and baked goods from crystallizing. But if you're fresh out of Karo, you can DIY a non-corn syrup that does exactly the same thing with just sugar, water, and a little cream of tartar and salt.
You'll need a candy thermometer to cook it to the right temperature; otherwise this recipe from The Kitchn is super-simple.
13. Ground flax or chia seeds mixed with water can replace eggs in baked goods.
Tori Avey / toriavey.com
The texture and flavor won't be exactly the same, but this trick will come in handy over and over if you're a vegan who loves to bake. Get the instructions here.
14. All you need to make self-rising flour is regular flour, salt, and baking powder.
A lot of Southern-style recipes (biscuits!) call for self-rising flour, but chances are it's not worth buying a bag that will then sit around until it goes stale. It's just as easy to mix up your own when you need it. Get the proportions for the mixture here.
15. It's easy to make custom-colored decorating sugar with regular sugar and food coloring.
This way you'll ALWAYS be prepared to have a cookie-decorating party, which is how it should be. Here's how to do it.