Actually, the people that boil the can without opening it first are not idiots but know what they are doing. If you submerge the whole can in water (at least an inch of water above the can) the can will never explode. Instead, you will be able to make the caramel in half the time, since it will be boiled under pressure. In two hours you will have semi-solid spread and in 3.5 a solid dessert. Plus it's easy, no need to open the can, find a foil, measure the water level. Just take the can and boil it. Voila.
You're right, this is an incredible sauce! I can remember doing this in college in the '70's, so it has been around awhile (ooo...I'm getting old!). At that time, warnings were abundant, regarding exploding cans, burns, etc. But I think the method you describe can be done safely. I think the previous idiots were trying to boil the can without opening it first (DUH!).
Previously I used to cook this (can unopened method) a lot, but as I like to see what I'm cooking, today I tried yet another method: pour contents of can into a sterile glass jar, the kind you would use for fruit or jam preserves. Close lid with ring in place. Put in a pot with water level an inch or so higher than contents of jar. Boil until desired shade of golden brown. It worked!! I think I boiled it for approx. 1 1/2 hours.
My father in laws mother used to make this for them when they little. His father used to work for the Borden milk company here in Nova Scotia and there was an unlimited supply of this milk in their home. After he told me about this, my girls and I used to make this as centers for chocolates for him every Christmas. Yummy.....
I make this a lot, but don't open the can. I just make sure it's completely under the water and turn it every 30 minutes to prevent burning on one side. Just let it cool and then open. I use this a lot for filling in chocolate cake. I just mix in broken health bar pieces. YUM.
After reading all the comments, I felt obligated to add my own to clarify. Dulce de Leche is originally from Argentina, not Brazil. Dulce de Leche is Spanish, not Portuguese for 'milk jam' or 'milk sweet'. It it was from Brazil, where the speak Portuguese, it would be called "doce de leite". Originally, my mother made it from scratch by boiling milk, sugar and a vanilla bean pod, stirring constantly for 8 hours. Now, we have an easy way to make it out of sweetened condensed milk in 2-4 hours, depending on the thickness you prefer. Yes, you boil a sealed can (or several), making sure they are fully covered with water at all times. If they are not fully covered with water at all times, they will explode and you will have caramelcicles hanging from your ceiling. The cans will now blow up as long as there are a couple of inches of water covering them. In Argentina, 'cajeta' is a dirty word, so don't refer to dulce de leche as 'cajeta' in Argentina. Cajeta is the term used in Mexico for this product. A little research will answer these questions for you. And yes, you can buy this product commercially in the United States. Most Walmart stores sell dulce de leche in the ethnic food isle. You can also purchase this only through Amigo Foods: http://www.amigofoods.com/dulce-de-leche.html and other resources. You cannot obtain the same results by using evaporated milk. That is a different product and does not contain the necessary ingredients to become dulce de leche.
I have never had Dulce de Leche before but have new neighbors from South America and wanted to make them something special to welcome them...so alfajores seemed like an easy one to try. So after deciding simple Dulce de Leche was best and reading the reviews I decided to try the UNopened can version of this, but was prepared to fall back to the slower version if needed. I set my timer every 15 minutes to make sure the water level was sufficiently over the cans and cooked for 2 hours, then I left the cans in the water with the heat off over-night to cool. When I opened them this beautiful golden creation greeted me. About the consistency of peanut butter and a small taste sent me reeling. How incredible! One can would certainly have been enough but I guess I will just HAVE to make some cake truffles with it too or maybe just a filling in a layer cake if I can keep my spoon from finding it's way to my mouth. Won't be the last time I make this!
My Mom used to make this! It makes wonderful caramel icing! Thanks for posting this recipe!
My husband was an AFS student in Argentina. He had this down there and since we have been married (20 yrs now) we have been making it, without opening it at all. No I am not dumb for doing it that way, that is the way they have showed him. Nothing happens, just make sure that you have water over the top and keep turning the can for even cooking. I love it on saltines. People can't believe how simple it is to make when they taste it.
Ok, I feel guilty, I cooked the sweet milk to a boil,then lowered it after it boiled and kept whisking for 10 minutes..and it was done. I used a non-stick pot & non stick whiks..as I removed it(very hot) I strained any particles that may have scorched into another bowl. Logically, I decided not to bake & just eat the bowl.