Preheat oven to 180 degrees C. Grease and line with baking paper two 23cm round pans.
Combine the crumbs, 1/2 cup pecans, flour, baking powder and salt.
In a large bowl cream the butter and the light brown sugar until fluffy. Slowly beat in the egg yolks, one at a time. Stir in the vanilla. Alternately add the milk and the crumb mixture while beating on low.
Beat the egg whites in a bowl until foamy. Add the sugar slowly and beat to soft peaks. Fold into the crumb batter and pour into the pans.
Bake for 25 minutes, or until a knife comes out clean. Cool in the pans on a rack about 10 minutes then invert and cool completely.
To make icing: In a saucepan over medium heat melt the 2 tablespoon sugar until it turns golden. Remove from heat and add 4 tablespoons of the butter; swirl. Whisk in the dark brown sugar and place back on the heat. Bring to a boil, stirring all the time. Add the cream and bring back to a boil. Boil 1 minute and remove caramel from heat.
Place the icing sugar in a large bowl and, mixing on medium speed, slowly drizzle in the caramel. Beat until the bottom of the bowl is just barely warm, about 5 minutes. Add the remaining butter 1 tablespoon at a time. Beat until smooth and chill icing until ready to ice the cake. Ice the cake and press the pecans into the sides.