I confirm this as a physics PhD. I also understand exactly this thinking of assuming a system is in thermal equilibrium where it is far from it (like a chicken in am oven).

You need the chicken to be 165F or 74C to be food safe. It takes a long time to cook at 100-200C because the heat is being transferred much slower. If we're using this instant slap-based cooking method, it only needs to get to the food safe temperature.

Using the OP's calculations and a cooked temperature of 74C:

It would take 8315 average slaps

or

A slap at around 813m/s or 1819mph.

*Edit for a correction to the second calculation (it still might be wrong), also, I rounded the numbers to whole integers.