Arrange the walnuts on a baking sheet and toast in the oven, shaking once or twice, until golden-brown, about 10 minutes. Remove from the oven and cool completely.
Preheat oven to 356°F (180°C).
Chop walnuts or lightly ground in a blender or a food processor.
Separate the egg whites from the yolks. In your stand mixer bowl (or hand mixer) beat the egg whites into a light meringue. Keep it in the same bowl or transfer it to another, if you want to continue with the same bowl. Store in the refrigerator.
In a mixing bowl add the butter and the sugar and beat until fluffy for at least 10 minutes. Add the yolks one-by-one and beat until absorbed. Add the chopped walnuts and the breadcrumbs.
Dissolve the baking powder in the cognac (or orange juice) and add it to the mixture. Add all the spices. Beat for a few seconds just until all ingredients mixed together.
Remove the mixer’s bowl from stand and add gradually the meringue into the mixture. Use a silicone spatula or just a spoon to slowly and gently fold the mixture together. Move from the sides of the bowl to the center and repeat until all meringue incorporated. The final mixture has to be soft and fluffy.
Brush a 9x7 inch (24x19 cm) cake pan* with butter and pour in the mixture. Spread gently only the surface. Don’t mix or press the mixture. Bake at 356°F (180°C) on a middle rack in the oven, for approximately 45 minutes.