Preheat oven to 350 degrees. Line large cookie sheet with parchment paper.
Combine flour, baking powder, baking soda, cinnamon and salt in a bowl. Whisk ingredients together. Set aside.
Using an electric mixer, beat the butter and both sugars until creamy.
Slowly add one egg at a time to the butter and sugar mixture, beating after each addition.
Add vanilla beating to incorporate with the butter, sugar, and egg mixture.
Slowly add the flour mixture, one cup at a time, stirring to combine after each addition.
Mix in the chocolate chips, stirring to add.
Next, add the white chocolate chips, stir well to mix.
Add in the peanut butter chips, stir well. Add both oatmeal and walnuts continue to stir to mix well.
Using a ¼ cup, scoop out the cookie dough and place on the lined cookie sheet allowing space for baking between each cookie.
Bake the cookies for 15 minutes or until the edges of the cookies are lightly brown.
Remove from oven allowing to cool slightly before transferring the cookies to a wire rack to cool completely.
Once each cookie is cool use your black decorating icing to glue on the eyes.
Next, outline the mouth and fill it in with the rest of the black decorating icing.
Set aside to allow the icing to dry.