Beat egg slightly set aside 2 teaspoons of egg. Stir tuna, onions,cheese, parsley, celery salt, and pepper into remaining egg.
Stir baking mix and water into soft dough, knead dough 5 times then roll onto flour surface and roll into a 15x10" rectangle. Spread tuna mixture on top.
Roll this up and make into a ring. Use shears to cut diagonal cuts in to top of ring. Brush top with reserved egg. Put in oven and bake 375 degrees for 30 minutes. Serve with cheese sauce on top.
For Cheese Sauce . Melt margarine and blend in bisquick mix,salt and pepper,cook over low heat until smooth and bubbly . Remove from heat and add in milk and cheese. Put back on stove, stirring constantly until cheese has melted and thickened.