Preheat oven to 325°F (160°C). Line a 6-cup muffin tray with paper or silicone liners.
Crust: process ½ cup rolled oats + ½ cup walnuts to fine crumbs. Mix in 1 tablespoon sugar, 2 tablespoon melted butter, pinch salt. Divide, press, bake 6–7 minutes until lightly golden; cool.
Filling: beat 6 oz (170 g) softened cream cheese 1 minute.
Mash ½ large ripe banana to ¼ cup (50 g); add to bowl with 3 tablespoon sugar (or 2 tablespoon honey/maple), ½ teaspoon vanilla, 1 tablespoon sour cream or Greek yogurt, ¼ teaspoon cinnamon, and 1 tablespoon flour or cornstarch. Beat until smooth.
Beat 1 egg separately; fold in by hand just to combine.
Portion into crusts; bake 20 minutes until set with a slight jiggle.
Cool 30 minutes, then chill 4–6 hours (overnight best).
Topping (optional): whip ½ cup cold cream with 1 tablespoon icing sugar to stiff peaks; pipe/spoon on. Garnish with toasted coconut and a banana slice.
