This is an old Polish traditions dating back to the 14th century.
On Holy Saturday people bring baskets of their Easter fare to church for a special blessing for all the different Easter foods.

The basket is traditionally lined with a white linen or lace napkin and should contain at least seven kinds of food, each with its own symbolism.
A Paschal Lamb, representing the Lamb of God, in Polish: baranek, can be made from cake, bread, sugar or butter and is often centerpiece of the food brought to the church. It symbolises the Passover offering of the Saviour.
Bread, ensuring good fortune is also a symbol of communion, the bread of the last supper. Cake symbolises skills and perfection.
Eggs, both decorated and plain, stand for re-birth, life's victory over death. Salt is a life-giving mineral, once believed to keep away all evil.
Smoked meat, usually ham or sausage (kielbasa), ensures health, fertility and abundance. Horseradish is a symbol of strength and physical fitness, bitter herbs signify the bitterness of the suffering of Christ.
Greenery, usually in the form of boxwood or branches of pussy willow represents the awakening of the earth.