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1
Frost the cake Preheat the oven to 350.
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2
Line a 9-by-3-inch round cake pan or springform pan with wax paper and grease the paper.
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3
(If using a springform pan that doesn't seal tightly, wrap the bottom in foil to prevent leakage.)
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4
Sift together the flour, baking soda, baking powder and salt.
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5
In the large bowl of a standing electric mixer, cream the butter and sugar at medium speed until smooth.
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6
Add the eggs one at a time, beating for 1 minute after each addition.
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7
In a bowl, mash the bananas with the buttermilk.
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8
Beat the dry ingredients into the butter at medium speed in two additions, alternating with the bananas.
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9
(The batter may appear slightly curdled.)
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10
Scrape the batter into the prepared pan and smooth the top.
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11
Bake in the bottom third of the oven for about 1 hour, or until a cake tester inserted in the center comes out clean.
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12
In a large bowl, using an electric mixer, beat the egg yolks and confectioners' sugar at high speed until pale and thick.
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13
Meanwhile, in a medium saucepan, bring the milk and banana to a boil over moderate heat, whisking occasionally.
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14
Slowly whisk the hot milk into the egg yolks.
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15
Pour the mixture into the saucepan and cook over moderately low heat, stirring, until thick, about 5 minutes; do not boil.
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16
Transfer the custard to a medium bowl and let cool briefly, whisking occasionally; then press a piece of wax paper directly on the surface and refrigerate until chilled, at least 3 hours or overnight.
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17
In a bowl, using an electric mixer, beat the butter at high speed until fluffy.
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18
Reduce the speed to low and gradually mix in the cold banana custard.
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19
Beat at medium speed until fluffy.
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20
Then beat in the espresso.
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21
Split the cake into 3 layers (they will be relatively thin).
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22
Place one layer on a cake platter and cover with half of the buttercream filling.
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23
Top with a second layer and the remaining filling.
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24
Place the third layer on top, cover with plastic wrap and refrigerate.
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25
In a large heatproof bowl, using an electric mixer, beat the sugar and egg whites until mixed.
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26
Place the bowl over a large saucepan of simmering water; do not let the bowl touch the water.
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27
Heat the mixture, whisking occasionally, until the sugar is dissolved, about 5 minutes.
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28
Remove from the heat and beat at high speed until fluffy, about 3 minutes.
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29
Beat the the meringue at medium speed until cool to the touch, about 5 minutes.
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30
Beat in the butter several pieces at a time, waiting until they are incorporated before adding more.
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31
Whip the frosting until fluffy.
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32
(If the frosting appears lumpy, beat at high speed until smooth.
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33
If the mixture is soft and runny, refrigerate for 5 minutes, then beat again.)
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34
Beat in the espresso and vanilla until blended.
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35
Set aside 1/2 cup of the frosting for decorating.
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36
Spread the remaining frosting on the sides and top of the cake.
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37
With the reserved frosting, using a pastry bag fitted with a star tip, pipe 8 rosettes on the top edge of the cake.
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38
Place 1 chocolate-covered espresso bean in the center of each rosette.
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39
To serve, slice gently with a serrated cake knife.
