Preheat oven to 180°C. Lightly grease a large loaf tin (23.2x13cm).
Prepare amaranth according to directions on the packet. Set aside.
Place 2 tablespoons of custard powder in a one-cup measuring cup. Fill with plain flour.
Place mix in a bowl and repeat with remaining 2 tablespoons of custard powder and plain flour.
To the flour add baking powder, walnuts and dates. Stir to combine.
In a separate bowl, combine bananas, honey, eggs, olive oil and vanilla. Beat until combined.
Add pre-prepared amaranth and mix well. Pour mixture over dry ingredients and mix until just combined.
Pour mixture into prepared pan. Bake for one hour.
Let cool in pan on wire rack for 10 minutes. Remove from pan and let amaranth loaf cool on rack.