Preheat your oven to 350°F (175°C). Generously spray a 12-count mini bundt pan with baking spray
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.
In a large bowl, cream the butter and granulated sugar together for 3–4 minutes until light and fluffy. Beat in the eggs one at a time, followed by the vanilla bean paste and mashed bananas.
Alternate adding the dry ingredients and the buttermilk to the wet mixture, beginning and ending with the flour. Mix just until combined to keep the crumb tender.
Divide the batter evenly among the 12 mini bundt cavities (filling about 2/3 full). Bake for 18–20 minutes, or until a toothpick inserted into the center comes out clean.
Let them cool in the pan for 10 minutes, then invert them onto a wire cooling rack to cool completely.
Whisk the instant pudding mix and cold whole milk together for 2 minutes until it begins to thicken.Place it in the fridge for at least 15 minutes to set completely. Beat the softened cream cheese and butter together until completely smooth and free of lumps.
Slowly add the powdered sugar and vanilla bean paste. Beat on high for 2 minutes until light, fluffy, and pipeable.
Transfer the frosting to a piping bag fitted with a large open star tip (like a 1M) or a large round tip.
Place your cooled mini bundt cakes on your serving platter. Spoon or pipe the chilled banana pudding directly into the center hole of each cake, filling it right up to the top.
Pipe a high-swirled rosette or a clean circular ring of vanilla bean frosting directly over the top of the bundt, completely covering and sealing the hidden pudding core.
Just before serving, press one fresh banana slice and one crisp vanilla wafer at a slight angle into the top of the frosting swirl.
