In a large bowl beat together the butter, brown sugar and granulated sugar until fluffy.
Add in the egg, molasses and vanilla and continue beating until combined.
In a separate medium bowl, whisk together the flour, cinnamon, baking soda and salt.
Add the flour mixture to the butter. Start with the the mixer on a low speed and then gradually increase to a medium speed until the ingredients are incorporated.
Turn the mixer down to low speed and beat in the oatmeal.
Stir in the chocolate chips and dried cranberries.
Cover the bowl with plastic and chill in the fridge for 1 hour or up to 48 hours (this is necessary or the cookies will spread too thin).
When ready to bake, preheat the oven to 350F (180C) or 325F (170C) on a convection oven (some ovens do this conversion automatically). Line cookie sheets with parchment paper or silicone baking mats.
Form the dough into balls with about 1.5 to 2 tablespoons of dough each. Place about 1.5-2 inches apart on a lined cookie sheet and flatten slightly.
Bake one tray at a time in the middle of the preheated oven for 9-11 minutes, or until the tops are just set. Allow to cool on the cookie sheet for 10 minutes, then transfer to a wire rack to continue cooling.
Optionally, place a few extra chocolate chips on top of each cookie.