Combine crushed vanilla wafers and chopped walnuts in a bowl. Line the bottom of a square 9-inch pan with half of the mixture.
In another bowl, thoroughly cream together the butter and sugar. Once creamed, add the egg yolks and beat well.
Melt the chocolate and add vanilla, once combined mix with the butter, sugar, and egg mix.
Whisk the egg whites until they are light and fluffy and form stiff peaks. Gently fold the egg whites in with the other ingredients. Be careful to not beat the air out of the egg whites.
Spread the chocolate mixture over the wafer and nut-crumb mixture. Then pour the remaining wafer and nut mixture on top.