In a large bowl, whisk the cold milk and vanilla pudding mix until a thick pudding forms. Add the condensed milk and vanilla, then mix until fully combined.
1/2 cup condensed milk, 3.4 oz instant vanilla pudding, 1 package, 2 1/2 cups cold whole milk, 2 tsp vanilla bean paste, or vanilla extract
Cover and chill in the fridge for 10 minutes. (This helps the pudding fully set and thicken.)
Meanwhile, add the heavy cream to a deep bowl and mix on high until light and fluffy with stiff peaks. (It should be like whipped cream.)
2 cups heavy cream
Remove the pudding from the fridge and, with a spatula, fold the whipped cream in the pudding until everything is fully combined.
Cover the bottom of the casserole dish with a layer of the pudding mix (about one-third of the pudding), spreading it evenly. (You can use a large or small casserole dish or any serving dish.)
Add Biscoff cookies (whole or halved) over the pudding mix, covering the entire dish. Top with sliced bananas, cut about 1/4 inch thick.
2 1/2 cups sliced bananas, about 6 medium bananas, 14 oz biscoff cookies
Add half of the remaining pudding mix on top, spreading it into an even layer.
Repeat with another layer of Biscoff cookies and banana slices.
Finish by spreading the rest of the pudding mix evenly over the dish, fully covering the cookies and bananas.
Cover the Biscoff banana pudding with plastic wrap and chill in the fridge for at least 6 hours or overnight.
Right before serving, top the Biscoff banana pudding with additional crushed Biscoff cookies and fresh banana slices. (Add the fresh banana slices just before serving to prevent browning.)
Serve and enjoy!