In a small saucepan combine the sugar, lemon juice, corn syrup and water. Bring the pot to a medium high heat. While doing this be careful not to swish the pan around because it could cause the sugar to recrystallize. As the sugar/water mixture boils the water will eventually evaporate and the sugar will begin to turn brown or to "caramelize". Pay close attention! Things can take a terrible turn for the worse here and there will be no recovery. As the sugar begins to turn a shade of golden, then light brown and then a slight shade of darker brown, remove it from the heat and add the heavy cream. As you do this, it will bubble up like crazy. Be sure to have a pot large enough to accommodate the bubbling up. Getting this on you could cause a very severe burn. Whisk the sugar/cream mixture until things settle down and add the butter 2 pats at a time, be sure the pats have completely incorporated before adding more butter.
Let cool and put into jars. Keep for about 10 days