In a mixing bowl, combine the banana flour, ground cinnamon, and sugar.
Add the cold cubed butter to the dry ingredients and work it in with your fingers until the mixture becomes sandy and crumbly.
Beat the egg lightly and add it along with a pinch of salt to the mixture. Stir well and knead gently until a dough ball forms.
Wrap the dough in plastic wrap and refrigerate for 1 hour to firm up.
Preheat the oven to 170°C (340°F).
Place the chilled dough onto a Silpat or baking mat and slightly flatten it. Roll out the dough to about 0.5 cm (1/4 inch) thickness.
Use cookie cutters to cut out desired shapes. Gather leftover dough, re-roll, and repeat cutting until all dough is used.
Arrange the cookies on a baking tray lined with a baking mat, spacing them slightly apart.
Bake in the preheated oven for about 12-15 minutes or until edges turn lightly golden.
Remove from the oven and let cookies cool on a wire rack before serving.