OATMEAL CHOCOLATE CHUNK COOKIES

1. Preheat the oven to 375° / 190°c. Line three baking trays with parchment paper.
2. In the bowl of a stand mixer fitted with the paddle attachment, beat the butter, brown sugar, and muscovado sugar on medium high until light and fluffy, approximately 4 minutes. Add the egg and vanilla, and beat until combined. Scrape down the bowl to ensure it is evenly incorporated.
3. In a medium bowl, whisk together the oats, flour, baking soda, cinnamon, and salt. Add to the bowl of the stand mixer, and mix until just combined.
4. Remove the bowl from the mixer and add the chocolate, incorporating by hand.
5. Scoop the dough into 2 Tbsp balls (I used a #16 scoop). Roll into balls with your hands, and space evenly on a baking tray. (I fitted about 8 per sheet).
6. Bake the trays, one at a time, for 10 to 12 minutes, or until golden brown. Sprinkle with flaky sea salt as soon as they come out of the oven. Allow to cool on the tray for 5 minutes, then transfer to a wire rack to cool completely.
7. Repeat the baking process with the remaining baking trays until all of the cookies are baked.

MASCARPONE FILLING AND ASSEMBLY

1. In the bowl of a stand mixer fitted with the whisk attachment, beat the butter, mascarpone, vanilla, and salt on medium speed until combined, 2-3 minutes. Add the sifted powdered sugar, and beat for a further 2 minutes, until light and fluffy.
2. Transfer to a piping bag fitted with a french star tip (I used Ateco #865).
3. Pair up the cookies into pairs of equal sizes. Pipe a round of filling onto one half of the cookie, and sandwich with the second half, pressing down gently.
4. Refrigerate until serving. Store leftovers in an airtight container in the fridge.