Food is the building block of life, any living entity when born cannot survive without food and nourishment. God has made such arrangements that the food of that living entity comes into the planet before even the living entity does. Thus food is very dear to us became a worthwhile of offering to God as gratitude. This sacrifice later took the form of Prasadam during the Puranic era. Prasadam means a gracious gift, a devotee offers food, clothes, or anything he wishes and considers acknowledged.
Anything that is acknowledged by a mere glance of God either by physical offering or mental offering becomes the Prasadam. In Bhagavad Gita 2.65, Krsna glorifies Prasad to be the destroyer of all miseries, prasade sarva-duhkhanam hanir asyopajayate. “The devotees of the Lord are released from all kinds of sins because they eat food which is offered first for sacrifice. Others, who prepare food for personal sense enjoyment, verily eat only sin.” (B.G 3.13)
The Srimad Bhagavatam says that if someone eats Prasadam unknowingly, sinful reactions of seven lifetimes are counteracted. If someone does that knowingly, sinful reactions of one million lifetimes are counteracted. The Vishnu Purana says that simply by honoring Prasadam once, one gets the credits of fasting for 6 months. The Brahma Vaivarta Purana says that when a person is full of Prasadam and he walks on the earth, he purifies the earth; when he goes to the holy place, he purifies the holy places; when he touches someone, that person is purified. Honoring Prasadam is equivalent to performing millions of Ashavamedha.
Such are glories of Prasadam. Devotees are eager to have Prasadam and only desire to eat Prasadam and nothing else. In Jagganath puri, Goddess Parvati in the form of Vimla eats only Mahaprasada of Jagannath. The goddess is described as surviving on the remnants (Uchchhishta) of Jagannath’s meals. There are no separate offerings are cooked for goddesses. Only Mahaprasad of dried rice mixed with grated coconut, paneer, curd, and butter is offered.
Only during the Durga puja non-vegetarian offerings are made and animal sacrifices performed in secrecy during pre-dawn hours before the opening of the main Jagannath temple. Devotees of Jagannath are barred from witnessing the worship and offering and only a few who witness the ceremony are given the Bimala parasada.
According to a narrative, Once Shiva went to visit Vishnu in Vaikhunta, he saw that Vishnu had just finished his meal, and a few rice grains had fallen on the ground. Spotting the Mahaprasada of Vishnu he quickly picked up the grain and ate it. Unknown to Shiva a half grain of rice had stuck in his beard. When Shiva returned to Kailash he saw Narada waiting for him, As soon as Narada spotted the half grain of Mahaprasada he quickly ate it. This angered Paravati as she missed her rightful share of Mahaprasad. She rushed to Vishnu to complain. Vishnu pacified her and promised her that during kali yuga when Vishnu would reside in puri as Jagannath, Parvati would reside as Vimala, and daily she would honor Mahaprasad of Jagannath.
After reading the story a question may arise, why does Shiva the supreme being according to Saivites need to honor Vishnu prasadam, and why Adi Shakti would want to live on Mahaprasada of Vishnu? To this the Srimad Bhagvad (12.13.16) mentions nimna-gānāṁ yathā gaṅgā ,devānām acyuto yathā vaiṣṇavānāṁ yathā śambhuḥ, purāṇānām idam tathā. Just as the Gaṅgā is the greatest of all rivers, Lord Acyuta is the supreme among deities, and Lord Śambhu [Śiva] the greatest of Vaiṣṇavas, so Śrīmad-Bhāgavatam is the greatest of all Purāṇas.
In the Krsna Janma Khanda of Brahman Vivarta Purana Shiva speaks to the devatas
adhunaa pancha-vaktrena yan naama-guna-kirtanam
gaayan bhramaami sarvatra nishprhah sarva karmasu
With my five faces (Sadyojata, Vamadeva, Aghora, Eshana, Sadashiva) I chant His name and qualities while I wander everywhere without involving myself in anything.
sarva brahmaanda samhartaapy aham krtyunjayaabhidhah
schiram tapasaa yasya guna-naamaanu-kirtanaat
By reciting His name and qualities while performing my austerities for a long time, I have achieved the power to destroy all the universes and have conquered even death.
The puranas also say that both are non-different
शिवाय विष्णु रूपाय शिव रूपाय विष्णवे
शिवस्य हृदयं विष्णु विष्णोस्च हृदयं शिवः
śivāya viṣṇu rūpāya śiva rūpāya viṣṇave
śivasya hṛdayaṁ viṣṇu viṣṇosca hṛdayaṁ śivaḥ
Vishnu always helps Shiva by taking Mohini avatar, destroying Sati’s body so that Sati can be reborn, by killing Madhu Kaitab as Hayagriva. And Shiva always loves to enjoy the pastimes of Vishnu. Shiva comes to take darshan of baby Krsna, Shiva helps Arjuna to learn some war skills. Shiva is worshipped by Rama before marching to Lanka.
Therefore it would not be surprising that Shiva could not miss the Mahaprasad of Vishnu and Parvati getting angry for not getting her share.