1. Preheat your oven to 375 degrees F. Line a large baking sheet with parchment paper (or spray with natural cooking spray). Set this aside.
2. With a stand or hand-held mixer, cream the butter and sugars together at medium speed until creamy. Add the vanilla, egg, yolk, and molasses, scraping down the sides of the bowl as you go. Set this mixture aside.
3. In a medium bowl, combine the flour, baking soda, cinnamon, and cloves. Whisk to combine evenly. Add the oats, and stir to combine. 
4. Add the dry ingredients to the wet, and mix just until combined. Using a small ice cream scoop or tablespoon measure, drop the dough in rounded balls on the prepared baking sheets; about 1.5 tablespoons of dough per cookie, placed two-inches apart on the cookie sheet. 
5. Bake for 10 – 11 minutes until the cookies are lightly golden brown around the edges. Cool on the sheets for a few minutes before transferring elsewhere.
6. Spread about 1.5 tablespoons of the filling (see instructions below) onto the bottom sides of half of the cookies, top with the remaining cookies, right side up. If you want them to be chocolate-dipped, dip the cookies into the melted chocolate and sprinkle with any decorations you like. Place the cookies back onto baking sheets to dry/harden before devouring. 

For the cream filling: 

1. With a stand or handheld mixer, beat the butter for one minute, until light and creamy. Add the powdered sugar and mix on medium speed for one to two minutes. Pour in the heavy cream/milk and the vanilla. Mix on high for 2 to 3 minutes, until fluffy. Taste and add a dash of salt if needed. If the filling is too thick, add a tablespoon or two of cream to thin it a little bit, to a nice spreading consistency. This should be thicker than a buttercream, for reference, and you will probably end up with more than you need, depending on how thick you like your filling.