Preheat your oven to 325 degrees F. Spray the bottom and sides of a 9x13" with with nonstick spray. Set aside.
Combine the sugar, brown sugar, milk powder, cornstarch and salt in the bowl of a stand mixer fitted with the paddle attachment. Mix on low speed until evenly blended.
Add the melted butter and mix on low speed for 2-3 minutes until all the dry ingredients are moist.
Add the heavy cream and vanilla and continue mixing on low speed for 2-3 minutes, or until any white streaks from the cream have completely disappeared into the mixture. Scrape down the sides of the bowl with a spatula.
Add the egg yolks on low speed, mixing them until they are just combined: be careful not to aerate the mixture but do be sure is is glossy and holds together. Mix on low speed until it is.
Add 1 cup chopped pecans.
Pour the filling into the prepared pan and bake for 8 to 10 minutes. You want the filling to be firmer and more set toward the outer edges of the baking pan but slightly jiggly and loose in the center. If the filling is still jiggly all over, give it another 2 to 3 minutes.
Use the filling right away, or store it in an airtight container in the refrigerator for up to one week.