Melt ½ cup (1 stick) butter in a microwave safe bowl and set aside to cool.
In a large bowl, add ½ cup brown sugar, ¼ cup sugar, 1 egg, 1 Tbsp molasses, 1½ cup rolled oats, 1 tsp cinnamon, 1 tsp baking soda, and ½ tsp salt. Stir together until combined.
Add the melted butter and mix until incorporated.
Add in 1 cup flour, and mix until cookie dough comes together.
Fold in chocolate chips (or raisins) as desired.
Scoop out 1 heaping Tbsp of dough and drop onto a parchment-lined cookie sheet. Press down to flatten slightly. Top with additional chocolate chips if desired.
Bake for 8-12 minutes or until edges are just barely browned Remove from oven and allow to cool before serving.