By THÉRÈSE MARGOLIS    

In Mexico, Christmas is customarily celebrated on Dec. 24, as opposed to the 25th.

And although Christmas Day is still the official holiday on the government calendar, it’s on the night before the birth of Christ that Mexicans come together with their families and friends to exchange gifts and fête the occasion with a gala dinner.

Although many Mexican families have adapted the custom of eating turkey for Christmas, the more traditional main course for the evening is bacalao, or codfish.

In keeping with the old Roman law of a meatless Christmas Eve menu, bacalao is usually prepared in a succulent Vizcaíno-style sauce of tomatoes, potatoes, olives and capers.

This marvelous dish is aromatic and satisfying, and is a definite party-pleaser for large gatherings.

Bacalao recipes vary from region to region, and most Mexican chefs like to add a secret ingredient or two to give it their own special flavor.

The main ingredient is, of course, dried cod, which must be soaked for at least two or three days prior to preparation in order to remove the fishy taste.

Most experts recommend using Norwegian cod, but less expensive bacalao is available if you are on a tight budget.

The codfish meal is often accompanied by “romeritos,” tiny rolls of dried rosemary sticks filled with potatoes and chopped shrimp.

These stringy croquets are chewy and sometimes hard to swallow, and, when doused with a generous quota of chocolate-based mole, can certainly be an exercise in culinary bungee jumping for the unindoctrinated.

But for those with a gastronomic sense of adventure, we have included recipes for both dishes.

Bacalao a la Vizcaina

2 kilos salt-dried Bacalao fillets (previously soaked in water for at least two days)

6 large peeled, tomatoes, chopped into bite-size cubes

1 chopped white onion

8 chopped garlic cloves

4 bay leaves (laurel)

1 cup virgin olive oil

1 small jar of green capers (alcaparras)

1 large jar of green olives

1 jar of sliced red peppers

1 jar of chiles in vinegar

12 small, unpeeled potatoes

Drain the codfish fillets and place them in fresh water. Set aside. Boil the potatoes in a separate pan until tender and add tomatoes, onions, olive oil and chopped garlic. Bring to a slow boil and then let simmer for about 30 minutes. Remove the codfish from the water and place in a large casserole dish. Cover the fish with the warm potato and tomato sauce mixture, and add the slices of red pepper, green olives, capers and bay leaves, Add chilies to taste. Place in a medium-hot oven and let cook for about 20 to 30 minutes, checking the fish frequently to make sure it does not overcook. Serve hot with white rice

Romeritos in mole sauce

24 small baby potatoes

1 teaspoon baking soda

10 nopal cactus leaves

1/2 kilo dried rosemary stalks

1/4 dried heads-on shrimp, peeled, shells and heads reserved

4 eggs, separated

8 tablespoons of cooking oil

1 jar of prepared mole paste

Place potatoes into a medium pot, cover with cold water and add a pinch of salt. Bring to a boil over medium-high heat and cook until soft. Drain, peel and set aside. Bring a second pot of water to a boil over high heat, add baking soda and cactus, and cook 10 minutes. Drain, then add to bowl with potatoes. Boil rosemary stems in a third pot about two minutes, until limp.

Simmer shrimp over medium heat until soft. Strain stock into a bowl, discarding shells and heads, and place drained shrimp into a food processor. Blend to a fine powder.

Beat egg white in mixing bowl until medium-stiff peaks form. Fold in egg yolks and shrimp powder with a rubber spatula.

Mold the shrimp batter into small flat mounds and fry to a golden brown. Carefully wrap each fritter with the rosemary stems.

Blend the mole and half of the shrimp stock in a blender and heat until warm.

Add mole to vegetables in bowl and mix well. Place the shrimp fritters in a large earthenware bowl and cover with mole sauce. Allow to come to room temperature before serving.