On a greased baking sheet, unroll crescent dough into one long rectangle, seal seams and perforations. In a small bowl, beat the cream cheese, onion and dill until blended. Spread mixture lengthwise over half the dough to within 1/2" of edges. Top with crab.
fold dough over filling:pinching seam to seal. Brush top with egg yolk. Bake 375 for 18-22 minutes or until golden brown. Cut into slices