5 eggs, for the Pentateuch: the foundation of our faith, and the beginning of God's work in the world. Eggs for new life; eggs to remind us what we have given up for Lent.
Butter! So much butter: 18 tablespoons, to be precise. Nine in each loaf of brioche. Six sets of three. Oh, the richness of the Trinity :)
Yeast, because we are Children of the Resurrection!
Flour and water--can't make bread without these.
Salt. We are the salt of the earth, after all.