Filling

1. Preheat your oven to 350F and grease an 8×8 baking pan.
2. Using a stand mixer with the paddle attachment, blend together the sugars, milk powder, cornstarch, and salt on low speed. If your milk powder is a little grainy, push it through a fine mesh sieve before mixing it in to help smooth it out.
3. Add in the melted butter on LOW speed until the dry ingredients are moistened. 1-2 minutes.
4. Add in the heavy cream and vanilla and continue to mix on low speed until white streaks from the cream have completely disappeared. Scrape down the bowl.
5. Add in the egg yolks a couple at a time on low speed until the batter is glossy and smooth.
6. Pour the mixture into your baking dish and bake for 3o-35 minutes. It’s done with the edges are golden brown and bubbling. It might seem a little too thin and buttery but it will thicken as it cools.
7. Let it cool to room temp them place it in the refrigerator for 4 hours or overnight. 
8. Once chilled, scoop out the filling from the pan (warning, it’s very sticky). Using an electric hand or stand mixer with the whisk attachment, mix your filling on medium speed until smooth. It shouldn’t take more than 1-2 minutes.
9. Using a teaspoon, scoop out the filling onto a plate lined with wax paper. You can also spray your spoon with some nonstick spray between each scoop since it’s very sticky. Place in the freezer while you make the cookie dough.

Oatmeal Cookie

1. Preheat the oven to 350F and line a large cookie sheet with parchment paper.
2. In bowl, combine your flour, oats, baking soda, and salt. Whisk to combine. 
3. Using a hand or stand mixer with the paddle attachment, cream together your butter and sugars until light and fluffy. 
4. Mix in your eggs one at a time and then the vanilla.
5. Slowly mix in your dry ingredients. It’s a very thick dough so near the end, I had to mix in the rest by hand. Make sure you get to the very bottom of the bowl because the dry ingredients like to hang out down there. Be careful not to overwork your dough.
6. Using a large ice cream scoop or 1/4 measuring cup, scoop out your cookie dough onto your baking sheet. Only bake about 4-5 at a time as they spread quite a bit.
7. LIGHTLY press them down with your palm. You don’t want to flatten them, just create a flat top for the filling to sit on. 
8. Top your cookies with the filling that’s been in the freezer and bake for 12-14 minutes. The edges should be a light golden brown but the center should still be a bit pale.
9. Let the cookies cool completely as the filling will need time to set again. You can either leave them at room temperature or speed up the process and place them in the fridge to set. 
10. Top with a dusting of powdered sugar and enjoy!