As Miss Beelzebub Likes it.
A Bit Bitter, Bibliomania; Go Forth, With Brownies.
S1 E5:
Mullin visits the Pandemonium Library with Azazel and runs into a sleepy bookworm and an ancient demon; Later, Belphegor wants an excuse to talk to Azazel, so she starts making brownies with Beelzebub.