You have to take the BK off the burner to add LME. Stir till no more LME can be scraped off the bottom,then return to heat. But youy can get caramelization,darkening,whatever you wanna call it easier with LME.
That said,I use plain DME in the boil for hop additions,Doesn't darken as easily as LME. Then add remaining DME & all the LME at flame out. Cover & steep 10-15 minutes to pasteurize,which happens around 162F. Works well for me. I get lighter colors & cleaner flavors...provided ferment temps are in check,etc.
Everything works if ya let it-Roady(meatloaf)