Lightly grease a 2 quart metal container or a clean 1 pound coffee can. Pick over whole cranberries, wash and drain.
Sift together the flour and salt; dredge cranberries in flour mixture.
Dissolve soda into boiling water and add molasses. Stir and allow to foam up.
Add to the flour and cranberry mixture. Mix together until well blended. Spoon into a greased metal container; cover with a double layer of tinfoil and fasten with heavy elastic band or string.
Place into a deep saucepan and fill with water up to about the half way mark on the pudding can. Cover pan and place over high heat. Bring water to boil, reduce heat and simmer for one hour. Remove from water and allow to cool. When ready to serve, invert pan or open bottom of can and push through. Slice in 1/2 inch pieces.
Prepare the sauce by mixing together the sugar, butter and cream. Cook over medium heat until thick, stirring constantly. Add vanilla and pour over individual slices of pudding.