I made my own dulce de leche for alfajores using the boiling water method. I also looked at other websites for using the boiling water method. Before I go into the details of my experience, I have to say that the result was delicious, and 2 cans of sweetened condensed milk cost a lot less than 2 cans of ready made dulce de leche. Homemade requires time but not constant attention. I haven't used the oven method but might give it a try sometime. Here's my experience with pros and cons of the boiling water method vs. what I think are likely to be pros and cons of the oven method. A big caution with boiling sweetened condensed milk in the cans is the risk of the cans exploding. So there ARE risks for damage or injury with this method. (The label on the product I last bought included a warning about not heating the sealed can -- probably so they wouldn't be held liable.) Other sites mention ways to reduce this risk: keep at least 2 inches of water above the top of the cans and add boiling water every 30 minutes or so to maintain that coverage. (If the cans stay well covered by hot water, the temperature stays at the boiling point of water. The risk of explosion increases if the temperature inside the can rises above that point.) Related to that risk is the importance of letting the cans cool completely before they are opened because the hot milk will be under pressure. A drawback that the blog mentions is that one can't tell how much caramelization is going on inside the sealed cans. I cooked the cans (I made two) at a LOW boil/simmer for 3 hours and probably could have cooked them longer (say, 3 1/2 hours) for a deeper brown color. I also took the cans out of the water bath to cool. I suppose I could have let them cool in the water and the milk would have continued to cook from the residual heat. A big advantage to boiling the milk in the cans is they can be kept at room temperature until they're ready to be used; some websites I saw said the cooked milk could be kept in the sealed cans at room temperature for up to 3 months; I doubt they would stay in my pantry that long. Living in the South, another advantage I see with the boiling water method is that it doesn't require heating an oven for hours to make dulce de leche. I also suspect that a lot of the energy that's used in the oven method is wasted heating the air inside the oven and in venting to the outside. I mentioned making more than 1 can at a time. Hey, if I'm going to spend 3+ hours making dulce de leche, I might as well make it worth my time. That requires less space in a pot on the stove top than in pans in a water bath in the oven. Some websites advise putting the cans on their sides in the water bath so that less water is needed to maintain an adequate level above the cans. Finally, some websites recommend removing the labels and cleaning the outside of the cans to remove as much residual adhesive as possible before putting them in the water. I hadn't seen that advice, put the cans with the labels in the water, and removed the labels when they floated to the top. I got a sticky ring of adhesive around my pan. The saving grace of this mistake was I learned that rubbing vegetable oil on the film and letting it stand helps to loosen the residue -- followed by a good scrubbing of the pan with a gentle cleanser such as Bon Ami and a scrubbing pad. However, it would be better not to deal with this mess in the first place. Regardless of the method, this is NOT a process where one can start cooking the milk and then step away to go run errands or spend a lot of time out in the yard and forget that you have milk cooking on the stove or in the oven.

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