In a large bowl, stir flour, baking soda, salt, cinnamon, ginger, and nutmeg to combine and set aside.
In another large mixing bowl, using an electric mixer fitted with a paddle or whisk attachment, cream the butter, brown sugar, and sugar on medium-high speed for about 3 minutes. Add the eggs and vanilla and mix until well combined, about 1 minute. Then add the flour mixture and mix on medium-low speed just until it comes together about 30-60 seconds. Mix in the carrots and oats to incorporate. Then add the pecans and mix just until well distributed. Cover and chill for 2 hours until the dough is firm enough to scoop and shape it easily.
Preheat the oven to 350°F/175°C (fan oven 330°F/165°C) and line two baking sheets with parchment paper. Set aside.
Scoop 2 tbsp (about 55g) of cookie dough per cookie onto the prepared baking sheets, 4-inch (10cm) apart, and flatten to about ½ inch thickness. Bake one sheet at a time for about 12-13 minutes or until the edges are set and browned, and the top looks matt and dry. Remove the cookies from the oven and let cool for about 5 minutes until they are firm enough to move them. Then transfer to a cooling rack and let cool completely. Once the cookies are cooled, prepare the frosting.
In a large mixing bowl, mix the butter on medium-high speed until soft and creamy, about 2 minutes. Then add the cream cheese and mix additional 1-2 minutes until well combined and no lumps remain. Mix in vanilla and powdered sugar until creamy, about 1-2 minutes. Fill the cookies with the cream cheese filling and serve. Store in an airtight container in the fridge for up to 2 days.**