Can you use soy milk in the place of regular milk at a 1:1 ratio in when cooking? I don’t know if it has the same properties when it boils, etc.
Thank you
Yes, pretty much. Sometimes the fat level will make a difference, so make sure you replace whole milk with a high (4%) fat soy milk, lowfat milk with a low fat soy milk, etc.
Some recipes - boiled puddings, e.g. - won’t work the same with soy milk, though.
How do you make soy milk?
You get up early in the morning, pull on the bean plant real hard…
I’ve used it in baking (chocolate cake, sweet potato pie, etc.), and had things come out just fine. (Interestingly, as long as the flavors mesh well, orange juice works as well - it’s very good in my favorite chocolate cake recipe.) I’ve never made my own - I just buy the stuff at the supermarket, there are a bunch of brands available, such as Soy Dream, Eighth Continent, etc.
However, soy milk chocolate pudding was horrible.
Yea, we tried soy milk Jello pudding, it just made a puddle of butterscotch flavored goo.
It usually works OK though (Silk brand here).
Ditto here with the pudding. Ugh.
I find soy milk is best in recipes that already have a kind of earthy, nutty flavour. Like bran muffins, carrot cake, etc.
Yeah Silk! 
And yes, it works quite well warmed. Has a slightly nutty flavor.