Chill your tools. Place your mixing bowl and whisk or beaters in the fridge for 10 minutes. Cold tools help the whipped cream set up nicely.
Make the instant pudding. In a medium bowl, whisk the cold milk and pudding mix for about 2 minutes until smooth and slightly thick. Let it sit for 5 minutes to fully set.
Mix in the sour cream and vanilla. Fold the sour cream and vanilla into the pudding.
The mixture should be silky and a bit tangy. Add a pinch of salt to round out the flavor.
Whip the cream. In your chilled bowl, beat the heavy cream with powdered sugar until soft peaks form. Don’t overwhip—stop when it looks smooth and holds gentle peaks.
Lighten the pudding. Gently fold half of the whipped cream into the sour cream pudding.
This creates a lighter texture that layers well. Reserve the rest for the top.
Prep the bananas. Slice the bananas just before layering to prevent too much browning. Aim for 1/4-inch slices for even layering.
Start layering. In a 9x13-inch dish (or a deep trifle bowl), add a layer of vanilla wafers, then a layer of banana slices, followed by a generous layer of the pudding mixture.
Repeat the layers. Continue with wafers, bananas, and pudding until you reach the top.
Make sure the final layer is pudding so the bananas are covered and don’t brown.
Add the whipped cream. Smooth the remaining whipped cream over the top. For extra flair, sprinkle crushed wafers or a dusting of cinnamon.
Chill. Cover and refrigerate for at least 4 hours, preferably overnight. Resting time softens the wafers and marries the flavors.
Serve. Slice or scoop and serve cold. Add fresh banana slices on top just before serving if you like.