If you don't have lemon juice
1 teaspoon of lemon juice = 1/2 teaspoon of white wine vinegar
If you don't have cake flour
1 cup of cake flour = 1 cup less 2 tablespoons of all-purpose flour
If you don't have buttermilk (because seriously, who does?)
1 cup of buttermilk = 1 cup of milk plus 1 tablespoon lemon juice or 1 cup of plain yogurt
If you don't have brown sugar
1 cup of brown sugar = 3/4 cup of granulated sugar plus 1/4 cup of molasses
If you don't have heavy cream
1 cup of heavy cream = 2/3 cup of milk plus 1/3 cup of melted butter
If you don't have ricotta cheese
1 cup of ricotta cheese = 1 cup of cottage cheese
And just for the record, I refuse to buy buttermilk. Because it never gets used unless it's for a recipe. And then I end up with a bunch leftover buttermilk to spoil in the fridge. So much easier to substitute.
What do you guys do? What ingredients have you found to substitute when you're in a pinch?