Danish pastry, n. — Green’s Dictionary of Slang

Danish pastry n.

[the ref. is to the pioneering operation undergone in Denmark in 1952 by Christine (formerly George) Jorgensen]

(gay) a transsexual.

1972		B. Rodgers Queens’ Vernacular 201: transsexual [...] Danish pastry.
1986–7		Maledicta IX 53: Danish pastry n [R] Transsexual; homosexual slang; from the pioneering operation undergone by Christine Jorgensen.
1997		(con. 1950s) D. Farson Never a Normal Man 195: And so chic, a real little Danish pastry.