7 eggs: 3 whole eggs and 4 egg yolks, at room temperature
1 cup buttermilk, at room temperature
For the Filling
1 jar (7 to 7.5 ounces) marshmallow cream
1/2 cup butter, softened
1 teaspoon pure vanilla extract
Confectioner's sugar for dusting (optional)
Spray a 12-cup Bundt pan with non-stick cooking spray and dust lightly with flour and set aside.
Sift together the cake flour, baking powder and salt and set aside as well.
Beat the butter and vanilla extract on medium speed until smooth and creamy.
Add the sugar and beat until evenly mixed, about one minute.
Slowly pour in the vegetable oil and beat until light fluffy, about two minutes more.
One at a time, beat in the eggs followed by the egg yolks.
Add the flour mixture and buttermilk in three alternating additions, beginning and ending with the milk,
Continue to beat on low speed until all lumps are removed, then fold by hand a few times before pouring into the prepared Bundt pan.
Bake at 325 degrees F for 60-70 minutes until golden and a wooden skewer inserted into the cake comes out clean.
Allow to cool in the pan for approximately two hours.
To make the filling, beat the marshmallow cream, butter and vanilla together until smooth.
Place in a pastry bag fitted with a round tip (a Ziploc bag with a corner cut off should serve in a pinch).
Use and apple corer or a knife to cut six deep holds into the bottom of the cake. Take care not to cut down through the top of the cake.
Use your fingers to connect each hole by burrowing down into one and across into the other. Dump crumbs as necessary.The goal is to create a tunnel within the cake.
Insert the tip of the filled pastry bag into each hole and gently fill. You should be able to see the filling start to fill an adjacent hole as it moves through the tunnel. If not, gently work the bag back and forth as you fill.
Scrape away any excess filling, invert onto a serving platter to remove from the pan, and dust lightly with confectioners sugar if desired.
I filled my cake just after the two hour mark. I tend to have the most luck removing cakes (and quick breads) from their pans when they have had a chance to cool but still remain warm.
Recipe by Love & Flour at http://www.loveandflour.com/cakes/so-long-hostess-hello-twinkies-bundt-cake