melt the chocolate in a double broiler or in the microwave - don't over heat - you don't want chunks but you don't want it to burn either
warm the corn syrup then add to the chocolate - stir until fully incorporated - but don't OVER stir - if it separates it's hard to bring it back together - I stir until it get's thick then I stop
lay out some plastic wrap and pour the modeling chocolate into it - wrap it up really good - but be careful not to get the plastic embedded in the chocolate (it will be hard to pull out once it hardens)
let sit over night!
the next day take a piece at a time and knead it - it will warm and soften in your hands
now I used 5 lbs of chocolate to make enough modeling chocolate for this cakea great part about modeling chocolate is it stays soft longer and doesn't crust over like fondant so you can keep working it longer and get the results you want (or fix mistakes)