“Nossa Senhora Dos Milagres’ themes are miracles, wishes and meditation. Her symbol is milk. ‘Our Lady of Miracles’ is likely a Christianized revamping of an earlier mother Goddess, as implied by Her sacred beverage, milk. Nossa Senhora dos Milagres grants the heartfelt wishes of those who give Her small offerings (often coins). This particular Goddess also mediates on our behalf with the gods.
Today’s catchphrase ‘got milk?’ takes on whole new meaning. It is customary to enjoy a banquet of milk and milk-based foods today to honor the Goddess and accept Her miracles into our lives [during Festa da Serreta].
Get creative as you want with this idea. For example, people having trouble with conception might request the miracle of fertility through an early morning eggnog. Those wishing love can eat cheese. Those needing to get the budget under control might make a rice pudding! Someone suffering from illness can eat ice cream with a blackberry garnish. All of these foods combine milk into a symbolic substance that releases the Goddess into the area of your life where She’s most needed.
To present a wish to this Goddess, just put a coin under your milk container in the refrigerator today and recite your desire. At the end of the day, give the coin to a young child or person in need so that the magic of happiness and kindness energizes your wish and the Goddess’s answer.”
(Patricia Telesco, “365 Goddess: a daily guide to the magic and inspiration of the goddess”.)
Specifically relating to today’s entry and event, the Festa de Serreta: “The Festa da Serreta has been held annually since 1932 in Gustine, California, is based on a similar festival held on the island of Terceira in the Azores, from which many of Gustine‘s residents emigrated. It is held in honor of Nossa Senhora dos Milagres, ‘Our Lady of Miracles,’ for whom a 16th-century priest built a small chapel in the Azorean village of Serreta.
The week-long festival attracts thousands of visitors. Highlights include the Bodo do Leite (‘Banquet of Milk’) fresh-drawn from the cows as is the practice in the Azores. There are also cantorías ao desafio (extemporaneous song contests), which draw contestants from all over California and even some Azoreans.
The image of Nossa Senhora is carried in a procession from the church to a portable chapel, or capela, that is brought out specifically for use on this occasion. A group of women sit in the chapel and watch over the donations of money that are left there. Another festival event is the traditional bullfight, which takes place in a rectangular arena. The bull is held by a long rope, his horns are padded, and the men do not so much fight him as play with him.” 
Answers.com, “Festa de Serreta“.
Wikipedia, “Nossa Senhora“.
Kathrynmaffei.tripod.com, “The Legend of Our Lady of Miracles“.