I'm a dumb@ss, but the result was cool. Don't try this at home!
This requires a plastic sight glass, and a busy brew day for best results.
Step 1: Set large (15 gal+) HLT on banjo burner
Step 2: Fill HLT with small amt of water (3 gal)
Step 3: Set flame on burner for a quick heat, and leave in charge of an assistant
Step 4: Get distracted for 15 - 20 minutes (fix some equipment, get lectured by SWMBO), forget that assistant has been enjoying homebrew.
Step 5: Run outside when you hear brew partner yell "I don't think that's supposed to happen."
Step 6: Carefully pull "modern art sight glass" off of HLT with vice grips, and replace with 1/2" threaded plug.