Preheat oven to 350 F.
Using a stand mixer, add room temperature vegan butter and coconut sugar. If you don't have a stand mixer, you can mix everything together by hand in a large bowl
Mix on a low speed for about 1 minute until incorporated.
Next, add eggs, molasses, and vanilla extract, mixing for about 30 seconds more.
Add flour, baking powder, cinnamon, nutmeg, sea salt, mixing for about 30 second more.
Finally, add the rolled oats. The dough should be pretty sticky.
Line a baking sheet with parchment paper.
Using a cookie scoop, form 12 cookies and spread them out, about 2 inches apart. If your baking sheet is small to accommodate all of the cookies, use two baking sheets or just bake them in two separate batches.
Gently flatten each cookie to about 3/4 inch thick. Bake for 12-13 minutes.
Remove from oven and let cool completely. This is VERY important!
Once the cookies have cooled cooled, make the icing.
In a medium bowl, whisk together the powdered sugar and water - it should be very thick.
Dip the top of each cookie into the icing and place it back on the baking sheet to set.
Store in an airtight container in the refrigerator for up to one week.