Children's fantasy about Easter and Gargoyles...

I know I should remember the name of a book I read any number of times, but I just don't... :(.
I think the story is set in an Austrian city; a girl is trying to solve a mystery which involves Easter and gargoyles and - maybe - a special Easter egg. She must solve it before Easter, when a gargoyle comes alive - or SOMEthing bad... Published around 1950.
Can someone please help me?

Is it _The Wicked Enchantment_ by Margot Benary-Isbert? First published 1955. :-)

touchstone: The Wicked Enchantment