Conflicting information about bechamel sauces
Chef John from Food Wishes just posted a new video about making lump-free bechamel sauces and he says, "Hot roux, cold milk, no lumps." This reminded me of the conflicting information out there about how to get a lump-free bechamel sauce. I've heard the hot roux, cold milk combo, and I myself use the hot roux, hot milk combo (as advocated by Julia Child). And I think I've also heard about every hot-hot, cold-hot combo there is. Why all the differences? And what combo will guarantee that you DO get lumps?
Bechamel making, along with roux-based sauces in general, have their rules and technique, but seemingly can be incredibly subjective. Chefs seem to have their favorite method, whatever works for them, what they were taught by whom ever. I do what I was taught in culinary school, hot roux, cold milk (although I use room temp or slightly warmed milk, to finish the sauce faster) and no lumps. I use the cold roux, hot milk combo when I have roux is made in advance and stored in the frig, by adding the cold roux to warmed milk, then whisk while heating the sauce.
I personally think you'll experience lumps when you don't whisk from the time you start adding the milk. I add a little milk, whisk out the sauce to blend, add a little more, whisk, then pour the remainder in slowly, continuously whisking, when the roux-milk mixture looks smooth and well blended, and then whisk frequently until the sauce thickens. No lumps. If you don't whisk in the milk slowly to start, and dump it in all at once, lumping will occur. Sometimes you can whisk the lumps out. Or just put the sauce in the blender for a few seconds or strain.
I don't believe there's any combo of cold/hot or otherwise that will cause lumps; it's proper, timely, continuous whisking that's most important for a lump-free sauce.
If you're getting good results from the hot/hot combo, use it. I believe that that particular style was not taught at school, as rapidly adding a hot liquid to a hot roux can result in splashing and burns. I've actually seen that happen in a few pro kitchens. Might be a different story at home, though.
Or strain it, that's what I did when I first started making it.
My mother can make it perfect with her eyes closed every time and it drove me nuts. I make the roux and go straight for the milk in the fridge adding gradually and mixing it as it warms up, then adding more and more... my mother adds it all at once and waits for it to thicken constantly whisking for 10 mins or so.
Do what works for you. Good luck!
I usually end up using hot roux, hot milk. Hot milk, because I was taught by some chef along the way to infuse the milk first with onion, bay, clove (and I use other ingredients depending on the final use). Gives a better tasting bechamel. Never have a problem with lumps. For me the trick is to add the milk small amounts at a time while whisking thoroughly.
I think cold-cold is the least likely to work.
We're told not to do hot-hot, because of the splashing thing. Usually it ends up being warm roux, start out with a little bit of cool milk, then add the majority of the warm/hot milk.
With enough whisking, though, I think any combination will work out in the end.
Concur that adding slowly and incorporating continuously is far more important than temperature. Warmed milk is better, but only because it means you've taken the time to infuse the milk with good things like bay leaf and onion or whatever is appropriate.
FWIW, I often use the Joy of Cooking method that finishes in the oven. It's so nice to ignore it and focus on the rest of the meal, or conversation.