Aromatic vegetables add flavor
The flavor base for stuffing starts with a mirepoix (pronounced meer-PWAH)—an assortment of chopped vegetables and seasonings cooked slowly in butter, oil, or rendered bacon fat. The idea is to soften the vegetables just enough to release their flavors; you want to leave them, especially the celery, a little crunchy to counter the softness of the bread. Onions and celery are almost always part of this aromatic mix, but consider them a starting point. A bit of garlic is always welcome. Other possibilities include shallots, red and yellow bell peppers, carrots, leeks, and fennel.
Sage is the classic seasoning used in turkey stuffings. Thyme and parsley are great along with sage. So is rosemary, but use it sparingly so its strong, resinous flavor doesn’t overpower. Spices like ground cloves, allspice, nutmeg, or mace give stuffing depth, adding a touch of sweetness and warmth. Use just a tiny pinch, however: the spice flavors shouldn’t stand out.