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1
Preheat the oven to 350 degrees F. Lightly grease 2 (10-inch) cake pans with 1 teaspoon of the butter.
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2
Line the bottoms with parchment paper, and butter the parchment with the other 1 teaspoon butter.
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3
Set aside.
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4
Puree the bananas, sour cream, eggs, and vanilla in a food processor.
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5
Sift the cake flour, 3/4 cup sugar, baking soda, baking powder, and salt into a bowl.
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6
In the bowl of an electric mixer fitted with a paddle attachment, cream the remaining 10 tablespoons butter and 1 cup sugar.
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7
On medium speed, add the dry ingredients in 3 additions, alternating with the banana mixture, scraping the sides of the bowl and beating well after each addition.
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8
Pour the batter into the prepared pans.
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9
Bake until the cake is lightly browned and bounces back when touched with your fingers, about 30 to 40 minutes, depending upon your oven.
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10
Let cool for 10 minutes before turning out onto a wire rack to cool completely.
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11
Peel off the parchment paper.
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12
To assemble the cake, using a long serrated knife, trim off the rounded top of each cake layer to make them flat.
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13
Place the bottom layer on a wire rack set over a baking sheet.
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14
Spread the Pastry Cream evenly over the top.
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15
Place the next cake layer upside down on the first.
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16
Wrap the cake around the sides with double layers of plastic wrap to keep the pastry cream from oozing out.
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17
Gently press down on the top layer.
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18
Remove the plastic wrap and scrape off any excess pastry cream.
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19
Slowly pour 1 to 1 1/2 cups of the Chocolate Ganache onto the top of the cake, letting it run down the sides.
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20
Let sit for 5 minutes, then, in several applications, slowly pour on the remaining ganache until the cake is completely covered.
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21
Chill until ready to serve.
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22
Combine 2 cups of the cream, 1/2 cup plus 1 tablespoon of the sugar, and the vanilla seeds and bean in a medium saucepan.
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23
Bring to a gentle boil over medium heat, whisking to dissolve the sugar.
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24
Remove from the heat.
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25
Combine the remaining 2 tablespoons heavy cream, the remaining 2 tablespoons of sugar, the egg yolks, and cornstarch in a medium bowl and whisk until pale yellow.
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26
Slowly add 1/2 cup of the hot cream to the egg yolk mixture, whisking constantly until smooth.
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27
Add the egg yolk mixture back to the hot cream, and whisk well to combine.
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28
Return to medium heat, and cook, stirring constantly with a heavy wooden spoon, until the mixture thickens enough to coat the back of a spoon, about 5 minutes.
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29
Remove from the heat and strain through a fine mesh strainer into a clean container.
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30
Cover with plastic wrap, pressing it directly against the surface to prevent a skin from forming.
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31
Refrigerate until well chilled, about 4 hours.
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32
Whisk until smooth before using.
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33
Scald the cream in a small saucepan over medium heat.
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34
Remove from the heat.
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35
Put the chocolate in a heat-proof bowl.
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36
Add the hot cream and let sit for 2 minutes, then whisk until smooth.
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37
Let cool slightly before pouring over the cake.
