Set aside 6 whole Biscoff cookies and 4 wafers if using for garnish. Crush the rest into a mix of fine crumbs and pea-sized pieces (food processor, rolling pin, or sturdy bag).

If using cookie spread, warm it slightly until pourable: microwave in short bursts at half power, stirring, or heat in a small pan over low heat. Do not boil.

In a large bowl, whisk pudding mix with cold milk for about 2 minutes until smooth. Let stand 5 minutes so it begins to thicken.

Whisk in condensed milk, vanilla, and salt until no streaks remain.

Fold in thawed whipped topping until the mixture is uniform and fluffy.

Fold in all but about 1/2 cup of the crushed Biscoff (reserve that for topping).

Spoon a thin layer of pudding cream into each jar and tap gently to level.

Add a few banana slices, pressing some against the glass if you want visible stripes.

Tuck in broken wafer pieces if using, sprinkle a tiny pinch of cinnamon, then drizzle a little warmed cookie spread if you like.

Repeat layers until jars are almost full, ending with a cream layer.

Cover jars and refrigerate at least 4 hours for firmer cookies inside the cream, or overnight for a softer, more merged texture.

Top with reserved crushed Biscoff, a broken cookie piece or wafer, and fresh banana slices right before serving so the fruit looks bright.