Common Baking Substitutions

How often do you start a recipe and then realize you're missing an ingredient?  I imagine that all of you are more well-planned than I, but perhaps one of these common baking substitutions may come in handy in a pinch someday.  You may not have self-rising flour or buttermilk hanging out in your pantry or fridge, but you probably have the approximation.  It's wonderful to feel so resourceful!  

1 teaspoon Baking Powder = 1 teaspoon Baking Soda + 1/2 teaspoon Cream of Tartar

1 teaspoon Rapid Rise Yeast = 1 1/4 teaspoon Regular, Active Dry Yeast (use 25% more than called for)

Self-Rising Flour = 1 cup all-purpose flour plus 1-1/2 teaspoons baking powder plus 1/4 teaspoon salt

1 cup Light Brown Sugar = 1 cup white granulated sugar + 1 tablespoon molasses
1 cup Dark Brown Sugar = 1 cup white granulated sugar + 2 tablespoons molasses

1 ounce unsweetened baking chocolate = 2 tablespoons dry cocoa powder + 1 tablespoon vegetable oil or melted butter or shortening (or one of my favorites, coconut oil! : )

1 cup Buttermilk = 1 cup milk + 1 tablespoon white vinegar or lemon juice, mix and allow to sit for 10 minutes

*Note on lemons: I'll buy a bag of lemons and if I don't get through them fast enough, I'll juice them. Freeze the juice in an ice cube tray, pop out the cubes and put a freezer bag to have on hand.  I can't tell you how many times I've had a recipe calling for lemon juice and think "Rats, I don't have any lemons" only to remember I have a whole lot of lemon juice waiting for me in the freezer.  Plus, it tastes so much better than the bottles of lemon juice concentrate--do those taste like metallic furniture polish to anyone else?