Figuring out what to do with the leftovers from developing all of these recipes is a constant issue. My wife and I do our best to make use of everything I make, but let's face it, sometimes you're not going to find enough uses for five gravies before they turn. Coming off a labor-intensive wave of Thanksgiving recipes that produced more food than we could ever eat—even after inviting friends over to help—I wanted to take on a sauce recipe that has staying power and wouldn't be a problem to finish off. Dulce de leche seemed like the perfect answer—anytime we have some of this caramelized sweetened condensed milk in the house, my wife and I are unashamed of the way we'll just grab a spoon and work our way through an entire jar.
The only thing was that dulce de leche didn't seem to be much recipe to tackle—how much can you vary a formula that takes sweetened condensed milk and cooks it until thick and golden? So instead of messing with ingredients, I decided to pit a few popular methods of making dulce de leche against each other and, much to my own surprise, each produced their own unique results.
I started from a logical place, from scratch. Broken down to its essentials, this sweet Latin American sauce consists of only two ingredients—milk and sugar. As the two combine and slowly simmer over many hours, a combination of caramelization and the Maillard reaction give the sauce its brown hue while the heat evaporates most of the water from the milk, creating the silky smooth, syrupy texture.
I used a little trick I saw from Alton Brown and added half a teaspoon of baking soda to my milk and sugar once the milk was heated and the sugar was dissolved. The baking soda further promotes the Maillard reaction and helps prevent the proteins in the milk from coagulating, which would result in gritty texture.
I let the milk, sugar, and baking soda mixture simmer as low as possible, stirring occasionally, until it turned deep brown and was nicely thickened, which took just over two and half hours. While the sauce was still hot and viscous, I poured it through a fine mesh strainer to remove any unwanted chunky pieces that formed.
The final sauce was a beautiful deep brown with a texture that was thick, yet still pourable. It wasn't as intensely sweet as the versions I made with canned sweetened condensed milk, which let the rich and robust caramel flavor stand out more. All-in-all, I considered it a success, but damn, it took a long time.
Wanting to speed things up, I looked to the microwave next. This method uses one can of sweetened condensed milk in a container about three or four times the volume of the milk. This is important since the milk will rise significantly as it cooks in the microwave, and a bowl too small will overflow and create a seriously sticky mess.
I got started with a couple of minutes at medium power to heat the milk. Once it was warm, I took things a little slower and reduced the power to medium-low, whisking the sauce every couple minutes to keep it smooth.
Factoring in all of the stirring required, the microwave method clocked in at just over 20 minutes, but actually required more active time than making it from scratch. There was also a huge sacrifice in flavor and texture. The microwaved dulce de leche never browned to the extent that it did using other methods and it thickened up way too much. The flavor was closer to the condensed milk it started out as, with a slightly gritty texture that was so dense it was hard to even spoon out. I was trying not to waste any food, but I ultimately ended up having to toss this batch.
Frustrated by the microwaved results, I went back to the stovetop, but decided to employ a double boiler rather than simmering the sweetened condensed milk in pan directly over the flames. Delivering a more gentle heat certainly had a negative effect on time—this took over one and half hours to brown—but also required almost no attention except a quick stir every fifteen minutes or so.
The double boiler produced a beautifully fine-textured dulce de leche that had a nice caramel flavor, but was not as deep as the one I made from scratch. I could have pushed it further by allowing it to cook longer, but once it started to take almost as long as making it from scratch, the double broiler didn't seem to hold much of an advantage.
I turned to the oven for my final attempt. Doing some creeping around recipe sites and blogs, this seemed to be the most popular procedure out there, and for good reason. The oven method requires just slightly more prep, but once it's done, it's the least labor-intensive out of the bunch (not that any of these require that much work).
To make dulce de leche in the oven, I emptied one can of sweetened condensed milk into an 8x8" glass baking dish and covered it with foil. I set it within a second, larger baking dish, which I filled with enough hot water to reach halfway up the dish. I slipped 'em in a 425° oven and let the sauce cook for an hour.
The water bath delivered an even and low heat to gently cook the milk. After an hour it came out a deeper shade of brown than I got using the double boiler, but not as deep as the one I made from scratch. There was some slight graininess right out of the oven, but a little whisking took care of that quickly, yielding a sauce that was smooth and had the right dulce de leche rich caramel flavor, sweetness, and consistency.
The ease of the oven and great results had me sold, but with the exception of the microwave, the other two methods produced fantastic dulce de leches as well. I would normally worry about having three versions of a recipe sitting around in my fridge, but I'm sure we'll have no problem finishing these all off in the month or so that they remain in their prime.