For the Custard

Cup of Yum
1. Whisk the milk and half of the sugar together in a large saucepan set over medium-high heat. Bring the mixture to a boil, then reduce to low heat and simmer for 1 minute.
2. While the milk is simmering, whisk the egg yolks in a medium sized bowl. In a small bowl, combine the remaining sugar and corn starch.
3. Whisk the corn starch mixture into the egg yolks. Do not do this ahead of time - the eggs will solidify if they stand for too long after the corn starch is added.
4. Add ¾ cup of the warm milk mixture to the egg yolk mixture and whisk to combine into a smooth mixture. Once smooth, pour into the remaining milk in the saucepan.
5. Continue to heat on low, whisking constantly, for another 2-3 minutes, or until the mixture reaches 185°F. The mixture will substantially thicken. If the yolks begin to clump, whisk against the side of the pan to break them up.
6. Add the butter and vanilla and whisk to combine. Transfer to a bowl and cover with plastic wrap to cool. Place the plastic wrap directly onto the surface of the custard to prevent a skin from forming.
7. Once the custard has cooled to room temperature, spoon into a piping bag or zip-top bag. Set aside.

For the Cake

1. Preheat oven to 350°F. Generously grease a 10-cup Bundt pan with crisco and coat with flour. If using a silicone Bundt pan, do not grease. Set aside.
2. In a medium bowl, whisk the flour, cinnamon, baking powder, and salt together. Set aside.
3. To the bowl of a stand mixer fitted with a paddle attachment, add the butter and sugar. Beat on medium-high speed until light and fluffy, about 2 minutes.
4. Add the eggs and mix for another minute. Whisk in the milk and sour cream.
5. Gradually add the dry ingredients to the wet ingredients. Mix until just combined.
6. Pour ¾ of the cake batter into the prepared Bundt pan.
7. Cut off the end of the piping bag or corner of the zip-top bag. Pipe the custard in a circle in the center of the batter. Top with remaining cake batter.
8. Bake for 75-80 minutes or until a toothpick inserted into the sides of the cake (not directly in the center where the custard is) comes out clean.
9. Let the cake cool for 30-45 minutes in the pan. Before the cake is completely cool, remove the cake from the pan and place onto a cooling rack.
10. While the cake cools, make the topping. In a small bowl, combine the sugars and cinnamon.
11. While the cake is still slightly warm, brush melted butter onto a small section of the cake. Sprinkle or press the sugar mixture onto the buttered section. Continue this process until the entire cake is coated. Slice and serve!