I always buy ripe bananas as they are usually cheaper than the unripe green crap.
Sometimes they are so ripe I can only mash them as they would not even slice :) but I love their sweetness.
This "mash" can be used as a dressing on green salad leaves (rocket, watercress etc) or it can be used as a base for a fruit salad.
You will be surprised how little amount of mash will one banana produce - usually I use 5-6 bananas to do this.
5 ripe bananas
1 large lemon or two limes (juice and zest)
2 tablespoons of walnut or coconut oil (or any other nut oil)
2 tablespoons of raw agave syrup (or zylosweet or anything else you like to use)
a pinch of pink Himalayan salt
ground cinnamon, cardamom or any other sweet spice you have to taste
Peel and mash the bananas - I use my old potato masher for this.
Add all the other ingredients and mix well. It will oxidize as time goes but the taste will be better.
I use it as it is to dress green salads or mix in any diced / sliced fruit for an unusual fruit salad. It tastes great with strawberries, mangoes, pears or apples.
You may add a bit of cayenne if you would like a kick; a bit of sumac or mango powder will make it sour. Sometimes I add a bit of fresh ginger.
Also, when I prepare it with mangos or pears I usually add some chopped mint leaves as well - it tastes and looks great with the green bits.
You can add diced fresh pineapples and coconut flakes (yum).
Really, the possibilities are endless, just use your imagination (and your leftover fruit).