When you want to mix two liquids in cooking, when does it matter to make sure you mix Liquid A into Liquid B and not the other way around?

One case where it’s important is when you’re blending together a thick mixture and a thin one. Imagine. for instance, that you’re adding a dollop of sour cream to a bowl of tomato soup. If you drop the sour cream in and stir, the sour cream will break up into little clumps, but will have have a hard time evenly dispersing in the soup. Do do it properly, you’d want to start with the sour cream in the bowl and gradually stir in the soup (this would be an absurdly anal thing to do for a bowl of soup, of course, but you get my point). The “thin into thick” rule is pretty universally applicable.

Ahh this makes sense. My dad also believes heavily in infusions. Like when he makes hot chocolate from a mix he mixes a little bit of hot milk with the mix until it becomes a sludge. Then he pours the rest of the milk in. He says that way you don’t get clumps of dry stuff. he said to never just dump the mix into the milk.

Yep.

Well, if you’re making a black and blue you want to pour the blue moon in first. The Guinness comes next and it will layer nicely if poured gently over a spoon.

As far as pouring hot into cold for cooking? I never thought about it. Now I will.

Probably doesn’t apply to cooking, but in chemistry when one liquid is dangerous, you should pour the dangerous one into the safe one so that if splashing occurs, it’s the safe liquid that splashes.

The most important thing is hot oil-water. first water, then oil. Do it the other way around you are in for a world of pain.

For salad dressings, it helps to add an emulsifier, like mustard, to the vinegar first and beat it together; then whisk in the oil, drop by drop.

When making custard, you also have to pay attention to how you mix beaten eggs (or yolks)i to the hot mixture, in order to prevent scrambled eggs from forming.

“The most important thing to remember when making custard is to beat the egg yolks and sugar together in a separate mixing bowl and then pour the warm milk or cream over the egg yolk mixture into the mixing bowl rather than adding the egg yolks to the saucepan.

This is so that the eggs do not cook and scramble. Once the eggs and sugar have been blended into the milk, the mixture can then be returned to the saucepan and the custard is cooked very slowly until it thickens to a creamy consistency.” Source

With flan, you reverse the process by slowly pouring hot mixture over eggs while whisking.

@gailcalled – OMG The custard – I did that once. I addidentally made scrambled eggs with the mixture. BLEAH

You always want to temper any liquids that are going from cold to hot. What I do is add small amounts of the hot into the cold mixing each time in between each spoon full until the cold liquid is now warm then I mix them all together. I do this especially when making homemade yogurt otherwise you risk killing the culture if the milk is too hot or adding eggs to any hot liquid otherwise you will have scrambled eggs in your mixture instead of it being smooth.

Yes, it does. As explained above, hot into cold a little at a time, and also liquid into powder, as in chocolate milk.