Wash and dry the limes. Firmly roll each lime several times on the counter under your hand.

Optional: Using a Microplane or rasp grater, finely zest 2 of the limes for garnish, if using. Put zest in a covered container and refrigerate until ready to serve.

Cut each lime in half and juice to yield 5–6 tablespoons. Strain out any seeds.

Put the sweetened condensed milk into a large bowl and add the miso paste or pinch of salt. Whisk until incorporated.

Add the heavy cream and whisk well.

Add 5 tablespoons of lime juice and whisk for about 1 minute. The mixture should thicken almost immediately. Let sit 2–4 minutes until further thickened. Add the extra 1 tablespoon lime juice if needed for a pudding-like consistency.

Whisk in coconut milk and shredded coconut. Set aside.

Slice the bananas into ½-inch rounds, about 4 cups total.

In an 8x8-inch glass baking dish (or other 2-quart baking dish), evenly spread about ¾ cup of the pudding mixture on the bottom.

Top with ⅓ of the cookies followed by ⅓ of the banana slices.

Repeat layers two more times with a scant 1 cup of pudding, ⅓ of the cookies, and ⅓ of the bananas, ending with the remaining pudding on top. Make sure bananas and cookies are completely covered with pudding each time.

Cover the dish and refrigerate at least 4 hours and up to 24 hours. The cookies will soften the longer they chill.

Serve cold. Garnish with toasted coconut flakes, lime zest, and extra slightly crumbled cookies, if desired.