Sak (pronounced 'shak') is a very special vegetable dish. Literally the name can simply mean 'spinach'. But in India, and especially in Bengal, where there are many dozens of varieties of green leafy vegetables, Sak is far from ordinary. It has a special place in temple kitchens and the home cooking repertoires of devotees of Krishna and his most recent incarnation, Sri Caitanya Mahaprabhu.
Sri Bhaktivinoda Thakur, esteemed 19th century Vaisnava saint and profuse author, writes in a song glorifying the relishing of food offered to Krishna before partaking (prasada):
heno sak-asvadane, krsna-prema aise mane, sei preme koro asvadana jada-buddhi pari-hari', prasada bhojana kori', 'hari hari' bolo sarva-jan
"O brothers! One day at Santipura, in Sri Advaita's house, Lord Caitanya and Nityananda were seated at prasada. When Lord Caitanya tasted the green vegetables, He said, 'My devotees, this sak is so delicious! Lord Krsna has definitely tasted it. At the taste of such sak as this, love of Krsna arises in the heart. In such love of God you should take this prasada. Giving up all materialistic conceptions and taking the Lord's prasada, all of you just chant 'Hari! Hari!'"

Furthermore, Chaitanya Bhagavata, a much loved and respected Medieval devotional text composed in classical literary Bengali states:
"Mother Saci knows that Lord Caitanya is greatly satisfied with sak, therefore she cooked twenty different varieties. The vegetable known as sak is more fortunate that any other preparation, for the Lord eats it again and again. Slightly smiling the Lord takes His meal, speaking, the glories of sak to everyone.
The Lord says "this sak is called Acyuta, by eating the sak attraction for Krsna develops (at the time of eating, Lord Caitanya would call different kinds of sak different names of Krishna) by eating patala, bastuka and kala sak, one gains the association of the vaisnava's life after life. If one eats salinca or helanca sak, he remain free from disease and gets devotion to Krishna". (CB Antya 4.279, 293, 295, 298)
Yes I know this is rather elevated material, and I won't hazard to write much about it. Anyway, I received a letter recently which inspired me to share it with you, and the following recipe. It's based on a recipe by Yamuna Devi from her award-winning and wonderful cookbook 'Lord Krishna's Cuisine'.