On the Food Network program Unwrapped, it featured a segment on the McGriddles. The way they get the syrup in the pancakes is to use maple syrup crystals ( or Maple Powder - click here
). You can search online for them; some natural food stores carry them. Or, you can make them yourself. I did it by putting some store-bought maple syrup in a cast iron pan and heating it over medium heat. Once it started to bubble, I began to stir it and kept it moving. About 3-4 minutes later I spread the mixture over a silicon mat in a sheet pan. As the syrup began to cool, I began stretching it to incorporate air into it and to get it thinner. (Be careful, I burnt my finger doing it.) Eventually, I pulled the syrup into one, long rod (probably about a quarter of an inch thick) and let it cool and harden. Once hardened, I cracked the maple syrup (which was now like a hard candy) and sprinkled them into the pancakes I was making. Just use your favorite pancake recipe.

Hope this helps.