Boost on most induction isn't meant to go more than about 10 minutes. If your several might have been that long since you selected it, that might have been the issue. Also, if the electronics are overheating, boost may be programmed to go off, and if they're overheating a lot, the whole unit can go off in self preservation.

Was there anything in the pot? How much air space is there under the unit? If you open a door or drawer to let in cooler air for the electronics, that can help if it's overheating.

Was there anything in the pan? Boost is really for getting a fast boil and you said "smoke". I wouldn't heat an empty pan on boost, at least until you really know your cooktop, and I wouldn't want it to get to the smoking point (at that point the fat breaks down and becomes unhealthy in a whole new way). You can get the pan much hotter than it seems. I usually heat a heavy pan on 7-7.5 on a 2.2K element. It gets just as hot in the end, just a little slower, allowing the pan to expand and ease the stresses. Perhaps you could use an infrared thermometer to assess the surface temperature instead?

Since I learned to blacken on a wimpy stove, I learned to put the pan in the oven to heat. I wouldn't want to transfer that to a glass top, however, unless I heated it with another pot to lessen the thermal shock, and you shouldn't have to do that with induction.

Caramelization happens at 350°. Take into account that the meat (red, poultry, fish) is cool, and you'll want to start at 375-400°, same as frying, and can go as high as just under the smoke point of your fat. If you really want a really hot pan, go for it, but step it up gradually and be careful. Literally red hot is probably not a good idea. Remember you can chill the meat to increase the temperature differential. I don't know if it's true, but the received wisdom is that the fat sticks better if the meat is cool.

This was a heavy cast iron skillet, empty. I tried it on high without boost and it did the same thing. On my old electric cooktop, it would smoke from residual oil in the pan when it got really hot. I use it without any oil to blacken peppers. It shut off on 9 while I was blackening them when I tried later and put the peppers in earlier. There is plenty of room underneath the cooktop. I guess maybe it was hot enough without me realizing it. The cooktop did not go into protection mode, just shut off and the residual heat indicator flashed H before it went off. I could turn it on after it cooled down for a few minutes.

I believe all brands' "boost" goes off after 10 minutes.

The last time I tried it without using boost at all, had it on 9 and it still shut off itself after several minutes with peppers roasting in there.

Pre-heating an empty cast iron pan on boost or on the the highest induction settings is generally not recommended. Several reasons for this

One is that induction heats CI much faster than most other ranges do and that can lead to cracking the CI pans. The heat pattern in CI tends to be pretty uneven until fully preheated. Too rapid heating will stress the pans and sometimes cracks a CI pan. This also can happen with higher powered burners on pro-style gas ranges, too. We've had several threads on cracking CI over the years if you want to research it further.

Second, I'm not directly familiar with your Miele cooktop, but consider that when you get your empty CI pan over 500°F you are burning off all the seasoning. When you crank that burner up on boost or, you may be pushing your CI pan up over
650°F. Lead melts at 621°F. That is hot enough to trigger safety
shutdowns on many induction burners. If you need to really sear the bejesus out of meat, try a welding a torch.

Third, consider how much more powerful induction burners can be than burners on most older radiant electric burners. Coil burners usually topped at around 8" and 2500 watts. Pretty much the same story with radiant smoothtops, too, until recently. (Some of the newer models now go to 3000 watts). A boosted induction burner might be up around 3500 watts or more.

If you really like pushing your pans to very high heat, I'd suggest getting one of the infra-red "point and shoot" thermometers. They work great on cast iron. Aim for a target of 500° which should be more than sufficient for searing or cajun-style blackening. You may well find that you won't have to ramp up over a setting of 6 or 7 (out of ten).

My own preferred technique is putting the steaks in a stainless skillet in a low oven (say under 150°F maybe) for about 20 to 30 minutes. Also, sous-vide works pretty well. (Steaks -- bef, fish, whatever --- in evacuated ziploc bags in 130° water --- depending on how thick they are -- maybe takes less half an hour to get the whole steak there). Then crank your CI pan to 500F. Dry your steaks/fish/whatever with a paper towel. Searing them takes only about a minute or so per side.

Thanks, all great info. Sounds like I need a lower setting with longer time to allow the temps to distribute evenly. Once my 60k outside burner is hooked up, I'll do the really hot stuff outdoors.

If you are new to induction, I recommend starting off super slow. The power is deceiving as you don't have a big flame to help judge.

I haven't used boost with a cast iron on my Miele but I have used the negative to turn it on. This starts at 12 and definitely will smoke oil and burn things! I learned that lesson quickly. I do heat at 9 sometimes - usually not for too long as it is hot but at least several minutes. I've burned more things in the first month than I have on any other stove! I've never gotten an error message or shut off (except once for boiling over on the control panel). This is using a 12 inch lodge skillet on either the 9 or 11 inch hobs. Something seems off with yours to me.

What does "I have used the negative" mean?

I was thinking the same thing about the negative comment. Mine only goes up to 9. If you hit the - button and auto-heat is activated in the options menu, it will go to the highest power for a set amount of time (depends on power level selected) before reverting to the actual power level you pick.

Ooohh. Different ones then. Mine is the 36" cooktop. Sorry for the lack of clarity - yes I meant the auto heat. My top number is 12. I actually haven't left it on 12 that much - since using the autoheat with my skillet seems to burn things. Again, hasn't shut off, but was just more heat than needed. I think it only leave it at 12 for a couple minutes to autoheat though so I may not have left it on as long as you.