the formula for converting kinetic energy and thermal energy is 1/2mv^2=mcT.

the average human hand weighs about 0.4 kg, the average slap has a velocity of 11m/s(25mph), an average rotisserie chicken weighs 1 kg(2 lbs), has a specific heat capacity of 2720 J/kg*C, assuming the chicken has to be 400 F for it to be cooked, the chicken starts at 0 C (frozen).

1 average slap would generate a temperature increase of 0.0089 C. It would take about 23034 slaps to cook the chicken.