Into a bowl, sift together the flour, baking powder, baking soda, and salt. Add the butter and blend the mixture until it resembles meal. Stir in the ginger puree and juice, the brown sugar and the walnuts. Add the milk and stir until it just forms a soft sticky dough. Drop the dough by rounded tablespoons onto an unbuttered baking sheet and bake the biscuits in the middle of a preheated 425 oven for 15 to 17 minutes, or until they are golden. Makes about 18 biscuits.