After the snow cleared and we ventured out again, the missing snowthrower throttle knob was sitting on the far reaches of the driveway:
It’s a well-meaning, albeit totally ineffectual, expedient repair.
I put a channel around the slot for the throttle shaft to mimic the original design:
The fracture started at the end and worked its way back, loosening the knob’s grip on the shaft as it went:
Should my replacement survive the next 13 years, it’ll likely outlive the rest of the snowthrower:
If the original MTD choke knob didn’t have that fancy metal insert, I’d replace it just for pretty …
The Smell of Molten Projects in the Morning 
I never remember how much I’ve already shared, so I’ll say this: My Gilson Montgomery Wards snowblower, 7hp B&S, is from 1969, and runs great…..they seem to be pretty durable. There’s a good chance yours will last as long.
Well, I’m still using a Monkey Wards screwdriver after all these decades: there’s hope!