Preheat the oven to 350F and prep muffin tins with liners.
In a large bowl combine all the dry ingredients, whisk thoroughly, and set aside.
In a stand mixer cream together the butter and sugar. Then add the pumpkin puree and milk and mix well.
When this is completely mixed together, turn the mixer to low and slowly add the dry ingredients a little at a time.
Once the wet and dry ingredients are mixed, stir in the chocolate chips and optional walnuts.
Using a spoon or ice cream scoop, fill the muffin tins with batter. These muffins will not rise a lot so you can fill them nearly to the top of the liners.
Bake for 20-25 minutes, till a toothpick comes out clean when pierced into the center. Allow to cool before serving.