E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Glasse (Mrs. Hannah),
a name immortalised by the reputed saying in a cookery book, First catch your hare, then cook it according to the directions given. This, like many other smart sayings, evidently grew. The word in the cookery-book is cast (i.e. flay). Take your hare, and when it is cast (or cased), do so and so. (See CASE, CATCH YOUR HARE.)
Well make you some sport with the fox ere we case him.Shakespeare: Alls Well, etc., iii. 6.
Some of them knew me,
Else had they caused me like a cony.
Beaumont and Fletcher: Loves Pilgrimage, ii. 3.
First scotch your hare (though not in Mrs. Glasse) is the East Anglian word scatch (flay), and might suggest the play of words. Mrs. Glasse is the pseudonym which Dr. John Hill appended to his Cooks Oracle.