Line a cookie sheet with a silicone mat or parchment paper. Set aside.
In a large mixing bowl, cream together the butter and granulated sugar along with the brown sugar. Use a hand mixer to incorporate more air into the mixture.
Mix until nice and fluffy for about 2-3 minutes.
Add 2 eggs and mix until combined.
Mix in the ground cinnamon, nutmeg, ginger, and salt. Mix until all spices are incorporated.
Slowly add about 1/3 of the flour and oats and mix until there is no dry flour, continue until you have mixed in all flour and oats.
Take a cookie scoop, I used the OXO Cookie Scoop of 1 1/2 Tbsp. Scoop the dough into a ball and place it on the prepared cookie sheet leaving about 1 1/2 inches in between each. They will spread out.
Bake in a preheated oven for 10-12 minutes until the edges are nice and golden.
Let the cookies cool for 2-3 minutes on the pan, then transfer to a cooling rack to completely cool.
While the cookies are cooling, make the icing.
In a medium sized bowl, mix the powdered sugar, cream, and vanilla extract.
Mix until combined.
Take a cooled cookie, and invert it in the frosting to cover the top.
Place back on the cooling rack and allow the icing to set.
Serve.
Notes
The cookies keep well at room temperature for 2-3 days or in the fridge for 5 days.You can freeze them in a freezer-safe bag for up to 2 months. It's best to freeze them though without icing.