M&M Cookies

I love M&M cookies, and I'm still trying to perfect my own recipe. This one is very close! The cookie itself is a little too cakey for what I am looking for, but everything else is right on. 

Ingredients
1/2 cup butter, melted

3/4 cup sugar
1 egg
1 teaspoon vanilla
1 1/2 cups flour
1/2 teaspoon baking soda
1/2 teaspoon salt
2 1/2 cups M&Ms

Instructions
Preheat oven to 375 degrees. 
Melt butter in a saucepan. While the butter cools, mix together sugar, vanilla, and egg. Add in the melted butter. Gradually mix in flour, baking soda, and salt. Stir in M&Ms.
Spoon tablespoonfuls of dough onto the cookie sheets.
Bake for 12 minutes. Cool completely on the cookie sheet.
Yields 2 dozen