Monster Cookies

I got this recipe from my friend, Lindsay.  She brought them over for a KSU watch party and everyone could not stop eating them!  They were amazing!

When I made them they still tasted delicious, but the flattened out and were crunchy while hers were nice and thick and chewy.  What did I do differently?  Was it the type of butter I used?  Let me know if you have any suggestions...

1/2 cup butter
1 cup sugar
1 cup brown sugar
3 eggs
2 cups peanut butter
4 1/2 cups regular oats
1/4 teaspoon vanilla
2 teaspoon baking soda
3/4 cup light corn syrup
1/4 teaspoon salt
1 cup m&ms
1 cup chocolate chips

Cream butter.  Add sugar and beat.  Add eggs, peanut butter, vanilla, syrup and mix.  Add oats, baking soda and salt.  Stir in m&ms and chocolate chips.

Bake 350, 12-15 minutes.  In my convection oven I only baked them 7 1/2 minutes.