Irish fare. Dublin in Boston. Every day is St. Patrick's Day at Fleming's, where food ranges from pub grub to fancy fare

FOR anyone living in the Boston area, it doesn't take guesswork to figure out what holiday falls on March 17. This city's large Irish population hardly clothes its heritage in secrecy on St. Patrick's day. But it did take one young man a wee bit of time to figure it out.

``The first St. Patrick's Day I spent in Boston 13 years ago fell on a Sunday. I remember walking down Newbury Street. I just couldn't figure out why everyone was carryin' on so and wearing so much green!''

Well of course he'd be a bit confused. Sean Boylan had just come here from the old sod itself.

``It's all rather quiet on St. Paddy's day in Ireland, ya know,'' Mr. Boylan explained in brogue as thick as potato soup as we lunched at Fleming's, an Irish restaurant he manages in Waltham.

Some of the larger cities in Ireland have their St. Patrick's Day parades, Boylan pointed out, but added that ``there's a lot of American-Irish cops and tourists that come over to march. A lot of the festivities are promoted by the Irish tourist bureaus here in the US. St. Patrick's Day celebrates an end to winter there as much as anything.''

As far as the food in Ireland goes, he says, it varies.

``You can get everything from pub grub to more fancy fare in some of the top restaurants in Dublin and Belfast. But it is comin' on. It's becomin' altogether more continental in the big cities.''

Whereas many restaurants in Boston will acknowledge St. Paddy's Day with a token plate of corned beef and cabbage and a slice of soda bread, here at Fleming's every day is St. Patrick's Day, at least in the kitchen.

Oddly enough, in spite of the large Irish population in Boston, it's easier to come across a snake on the Emerald Isle than to find an Irish restaurant in this area.

``Irish restaurants here succeed in spite of the food. We're trying to succeed because of it,'' Boylan said as Felicity, our waitress from Westmeath, Ireland, served a starter course of thick, luscious pink folds of imported Irish smoked salmon with capers, Irish brown bread, red onion, and lemon wedges.

``We don't eat it with sour cream, just plenty of lemon to give it some `bite.''' said Boylan.

Although he doesn't particularly miss it, Boylan mentioned mutton as one staple of an Irishman's diet that's rarely available in the states. ``We eat a lot of pork, lamb, salmon, and beef too.''

And chicken? What do the Irish do with chicken?

``Chicken? We chase it until we catch it,'' he laughed.

The Irish side of the menu at Fleming's also includes Mullingar Style Beef Stew, Fish Pie `a la Fleming, Irish Saddle of Lamb, Gaelic Steak, Killybegs Style Fish and Chips, and a savory Shepherd's Pie.

``We use minced lamb, plenty of seasoning, and then pipe mashed potato on top of the Shepherd's Pie,'' says Boylan.

But you have to proceed with some caution when it comes to tradition, he says.

``Some older folks will get annoyed if you make anything a little different. And if it's too spicy they start questioning your ethnic origin.''

Although Boylan confesses that he likes to fire up a Chinese wok and whip up some Sichuan dishes at home, one look at his red hair and cherubic cheeks quickly puts the ethnic question to rest.

Here are a few recipes from Fleming's Restaurant. Potato Soup 2 tablespoons butter 2 onions, peeled and sliced 2 pounds potatoes, peeled and sliced 2 carrots, chopped 2 celery stalks, chopped 1 bay leaf 3 cups milk 3 cups chicken stock (or water) Salt and pepper to taste 6 slices lean bacon, diced and fried

Melt butter in a large saucepan, add onions, and saut'ee until soft.

Add remaining ingredients, cover, and simmer for one hour. Serves 6 to 8. Shepherd's Pie 3 tablespoons corn oil 1 large onion, chopped 2 ribs celery, finely chopped 3 carrots, finely chopped 1 pound ground lamb 1 beef boullion cube dissolved in 1 cup boiling water 1/2 teaspoon garlic, minced 1/2 teaspoon thyme 1/2 teaspoon oregano 1/2 teaspoon pepper 1/2 teaspoon salt 3 medium potatoes, peeled, cubed (or two cups left-over mashed potatoes) 2 tablespoons butter Milk

Heat oil in large frying pan and saut'ee onions, celery, and carrots until onions are limp. Add lamb and brown. Add beef broth and seasonings. Pour into oven-proof dish and bake, lightly covered with aluminum foil, in oven preheated to 375 degrees F. for 30 to 40 minutes. Check while cooking and add a bit of water if mixture tends to dry out.

Meanwhile, boil potatoes and mash with butter and a little milk to lighten texture.

Remove lamb from oven and adjust seasonings. Spread or pipe potatoes on lamb with a pastry tube. Place under broiler a few minutes until lightly browned. Serves 4. Slaney (Baked Trout) 4 trout (allow one per person if large, two if small) 3 teaspoons butter 2 teaspoons fresh lemon juice 1/2 teaspoon dried tarragon

Preheat oven to 375 degrees F. Trout should be cleaned, but head and tail left on. Place in buttered oven-proof dish. Melt butter with lemon and tarragon and pour over fish. Cover and bake about 20 minutes. Champ 4 to 5 scallions 3/4 cup milk Salt and pepper to taste 1 pound potatoes, mashed and hot 4 tablespoons melted butter

Cut up scallions (including green) and cook in milk until tender. Drain, reserving hot milk. Stir salt, pepper, and scallions into potatoes. Add hot milk and stir again. Make a well and pour a little butter into each serving of potato. Serves 4.