Lightly grease 6 moulds in a muffin tray and preheat the oven to 200°C.
Sift together the flours, salt, baking powder and soda bicarb in a bowl.
In a separate bowl, lightly whisk together the olive oil and sugar followed by the flax mixture, mashed bananas, vanilla essence and milk.
Now using a spatula, gently fold in the dry, flour mixture into the wet mix until almost combined. Put in the chopped walnuts and in just a few strokes, fold them into the batter taking care not to over-mix.
Rest the batter for 10 minutes and then fill the greased molds till three fourths full.
Bake in the centre of the oven for 16-18 minutes till the muffins are tall and golden. A toothpick inserted into the centre of the muffin should come out clean with no traces of wet batter. Cool in the tray for 5 mins before transferring them onto a wire rack to cool fully. Store in an air-tight container at room temperature for a couple of days. Refrigerate to keep for longer.