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1
Preheat oven to 350u00b0F.
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2
Butter 2 9-inch round cake pans; line bottoms with parchment paper. Butter the parchment and dust with flour, tapping out the excess; set aside.
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3
Into a medium bowl, sift together the flour, baking powder, baking soda, and salt.
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4
In a small bowl, stir together mashed bananas, sour cream, and vanilla; set aside.
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5
In the bowl of an electric mixer fitted with the paddle attachment, beat 1 1/2 sticks butter and 1 2/3 cups sugar on medium-high speed until light and fluffy, 3-4 minute Scrape down the sides as needed.
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6
Add the eggs, one at a time, beating well after each addition.
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7
With the mixer on low speed, add the flour mixture in two parts, beating until well combined after both additions, 2-3 minute.
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8
Using a rubber spatula, fold in the reserved mashed banana mixture, being careful not to overmix.
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9
Divide the batter between the prepared pans and bake 30-35 min, or until golden and a tester inserted in the center comes out clean.
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10
Transfer pans to a wire rack to cool for 20 minute.
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11
Invert cakes onto the rack; peel off the parchment paper and reinvert cakes, and let them cool completely, top sides up.
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12
Sprinkle 1/4 cup sugar into a large skillet; cook over high heat, shaking the pan occasionally, until sugar is caramelized.
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13
Remove from heat and stir in 3 Tbs butter until melted.
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14
Return pan to medium heat and add the sliced bananas. Cook until slices start to brown, 1-2 minute Gently turn the bananas, and cook over medium-high heat until browned, about 2 more minute.
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15
Using a serrated knife, trim the tops of the layers to make them level.
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16
Place one layer on a cake plate and arrange the caramelized banana slices on top. Make sure the entire top is covered.
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17
Place the remaining layer on top and frost with mascarpone frosting.
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18
To make the frosting:
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19
In the bowl of an electric mixer fitted with the paddle attachment, beat the mascarpone, cream and confectioners' sugar until medium-soft peaks form, about 1-2 minute Be careful not to overbeat, and use immediately.
