In a large bowl, whisk flour, baking soda and powder, salt and all the spices together. Set aside.
In another large bowl, blend together (with a hand mixer) the brown sugar and canola oil. Add in the pumpkin puree and blend until well combined.
Add in the eggs and vanilla.
Slowly pour the wet mixture in the dry mixture. Split it up into 2-3 batches. Blend until it is all combined, scraping down the sides of your bowl to get everything in.
Line your baking sheet with parchment or wax paper.
Use a tablespoon or a measuring cup (I used a 1/4 cup) and put the dough on the baking sheet about 2 inches apart. You can make them as big or little as you want. I opted for a heaping 1/4 cup of batter to end up with the size of mine.
Bake for 13-15 minutes. I baked mine for 13 minutes and they were perfect. If your toothpick comes out clean, you're good to go!
Remove from oven and let cool on cookie sheet for about 5 minutes then transfer them to a cooling rack to cool completely before frosting.
To make frosting: Combine all the ingredients in a bowl and beat with a hand mixer until well combined. It will be airy and fluffy. This may be made a day ahead and chilled until ready to use.