I have a recipe that required 320ml of Buttermilk but I only have 280ml. Can I use normal milk to make up the other 40ml? The shops are closed which is why I'm asking. The cake is just for a family member.

If you don't have buttermilk you can substitute.........1 cu whole milk pus 1 3/4 tsp cream of tartar, or 1 cup plain yogurt, or 1 Tb lemon juice or vinegar plus enough whole milk to make a cup-let stand 5 mins before using.

It depends on your recipe... But most likely it will be fine when it's such a small amount. Or you could use orange juice, again depending on the recipe. I have a very versatile recipe that calls for either buttermilk or orange juice.
The reason for using buttermilk (or orange juice) is that the baking soda needs an acid to work properly and to avoid an off-taste in the cake.

You can sub this for buttermilk...take 1 tablespoon lemon juice or 1 tablespoon white vinegar put in measuring cup, then add milk and fill to 1 cup mark...mix, let sit for 5 minutes or so and when the milk and acid react with each other it will look slightly curdled...But I think a small amout of milk would be ok.

Thank you all so much for your help. It is much appreciated!

Just a little FYI for next time. I keep a container of buttermilk powder in the cupboard for times I forget to pick it up or don't have it when I need it for a quick batch of pancakes--It's in the grocery store by the regular powdered milk or I have found it in the baking section as well. Hope they have it in Australia!

Oh Kansaslaura I am definitely going to look for that the next time I go to the store! I use buttermilk in my chocolate cake recipe and they only have the big one so I end up throwing most of it away, thank you!

I read in another post that you could freeze buttermilk and heavy whipping cream--I was not aware you could do that. So I froze my leftover buttermilk and cream and used both recently for a cake--it worked perfectly. I do not hesitate to buy large containers now that I know I can freeze the leftovers! I just hate throwing out anything--it is such a waste of money! It is so convenient to have them in the freezer!

YAY! I can freeze! I love you guys, haha! So does this mean I can freeze liquid coffee creamer? Please say yes!

I've done it and it was fine!

Yay again, thank you!

thanks for the thread i have tried 3 supermarkets today for buttermilk to try a recipe out , i dont think it must be used much in england, but now thanks to all you brill ccs i can substitute and i will start a hunt for poedered bm