Preheat oven to 325°F. Grease and flour two 9-inch round cake pans and set aside.

Beat the sugar and eggs together until they're light and fluffy, about 2 minutes at medium-high speed using an electric or stand mixer. Slowly beat in the vegetable oil.

Add the flour, salt, and baking powder to the egg mixture and beat until just combined. Use a rubber spatula to scrape the sides and bottom of the bowl to evenly incorporate. In a small bowl or measuring cup, whisk together the milk, butter and vanilla. Slowly add the liquids to the cake batter, mixing until everything is well combined. Fold in the sprinkles. The batter will be very thin, but that's okay.

Divide the batter evenly among the prepared pans and bake for 30 to 35 minutes, or until a toothpick inserted into the center comes out clean. Remove the cakes from the oven, cool them in the pans for 10 minutes, then turn them out onto a rack to cool completely.

To make the filling: In a medium-sized saucepan, stir together 2 cups of the milk, the sugar, and the salt. Bring to a simmer over medium heat, stirring to dissolve the sugar. In a separate bowl, whisk the cornstarch, egg yolks, and whole egg with the remaining 1/2 cup milk.

Whisk some of the hot milk mixture into the egg yolks/cornstarch to temper the yolks. This prevents curdling. Pour the egg/milk mixture back into the remaining simmering milk in the pan, pouring it through a strainer to capture any bits of egg. Bring the mixture to a low boil over medium heat (this may happen very quickly), stirring constantly with a whisk, and cook for 2 minutes; the mixture will thicken significantly. Remove the filling from the heat and stir in the vanilla. Transfer the filling to a heatproof bowl, and top it with a piece of buttered plastic wrap (make sure it touches the top of the filling so it doesn't develop a skin). Refrigerate until cool.

When the cakes and pastry cream are completely cool, spread the filling in an even layer over one layer then stack the second layer on top. Set aside.

To make the glaze: Melt the chocolate and cream together until smooth and lump-free. Add the vanilla and stir well. Let the glaze sit for about 10 minutes to cool a bit and to thicken slightly. Pour the glaze over the top of the cake and top with sprinkles along the edge of the cake. Serve immediately or refrigerate until ready to serve. Enjoy!