One, two, three: voila!

SELF-HELP happens in the strangest places. One day you’re walking home from the farmers market with four pints of different berries and you stop to pick up some cream to whip and the cashier is right next to a glass case lined with Technicolor fruit tarts and you think: I could do that, and better, for a lot less than $30. And I’m pastry-challenged.

That wouldn’t be just the berries talking, either. Fruit tarts are the right dessert right now, a big step up from plain watermelon and a lot cooler on the kitchen than peach pies, largely because the main ingredient is at its peak. But the other two elements, the crust and the filling, are both almost as effortless as finding perfect fruit.

Call it three easy pieces: You start with a tart shell that is simpler than pie crust, more like one big shortbread cookie. You fill it with a one-two pastry cream that makes instant puddings look turgid. And you finish with what waning August brings in such abundance: ripe fruit with voluptuous local flavor.

Pies are not my forte, but I’ve known tarts are a different story ever since restaurant school, where half the motivation of most of the students was finding ways to maximize profits on simple creations. Tarts are show-stoppers that take very little in terms of time, money or skill. Even the fruit is mostly a matter of garnishing -- arranging the berries over the cream -- than the drudgery that pie filling involves in other seasons, all that peeling and coring and slicing of apples and pears.

The best tart lesson in school was creme patisserie, as pastry cream was called by our Careme-worshipping dessert teacher. Making it is so simple: Heat milk and cream to a simmer, then whisk a little of the liquid into egg yolks beaten with sugar and some form of thickener -- flour, cornstarch, arrowroot -- and return that liaison to the pot and stir until it thickens.

In class, we used this magic mixture not only to fill tart shells to be topped with berries or ripe peaches or plums but also to stack puff pastry into napoleons, and pipe into cream puffs. Without the thickener, we could dispense with the tart shell and just serve the berries either under or over that rich, sweet cream.

Shell game

THE tart crust was always a lot trickier. I must have been dozing off when it was explained, because for years I was afflicted with pastry just as leaden as what lay sodden under my pumpkin pies. I could never get the proper proportion of butter to flour right, or keep a cold enough hand in mixing it and always wound up with more heaviness than flakiness.

Then I took a class with cookbook author Joanne Weir, of “Weir Cooking in the City” TV fame, in which a shortbread crust was key, from a recipe she had borrowed from Chez Panisse. It started with butter at room temperature and encouraged mixing by hand; it took away the fear of over-handling. Then it called for freezing the dough once it was in the tart pan, which eliminates the need for lining the shell with foil and weights when you bake it. I’ve made this repeatedly and it never fails. Even better, it is the closest thing to my Belfast-born mother’s Irish shortbread, which I have never been able to duplicate.

Weir flavored the dough with lemon zest, and the original Chez Panisse recipe used a couple of drops of vanilla and almond extract. Lime caught my eye after I read a recipe by legendary cooking teacher Madeleine Kamman that paired blueberries and bourbon with fresh lime.

Nearly flawless

MOST berry/fruit tarts are glazed with melted jelly, usually currant, for both structural and appearance reasons -- the gleam adds to their appeal and the sweet stickiness holds the berries in place. But I’ve lifted from Kamman and used lime marmalade. The sugary tartness is just right against the hypersweet late-summer berries.

The whole formula is pretty close to foolproof, but deconstruction is always an option. If you want to skip the crust, you can serve the berries with just the pastry cream spooned over or under. If you don’t want to make the pastry cream at all, make the crust and substitute whipped cream as a more ethereal filling. You could even bake the crust and not fill it, just cut it into triangles to serve as cookies with the fruit, either naked or cream-coated.

Even if the unimaginable happens and the crust cracks or the filling is too loose or too firm, you still come away with the rough equivalent of a trifle: pastry, cream, berries.

No wonder tarts in summer are so empowering.

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Summer fruit tart

Total time: About 1 hour, plus chilling and freezing time

Servings: 8

Note: Currant jelly may be substituted for lime marmalade, available at Surfas in Culver City and at Continental Shop and Tudor House, in Santa Monica, and the Cheese Store of Silver Lake.

1 cup flour

8 tablespoons sugar, divided

1/8 teaspoon kosher salt

1 teaspoon freshly grated lime zest

1/2 cup (1 stick) unsalted butter, softened

3/4 cup whole milk

3/4 cup heavy cream

3 large egg yolks, room temperature

1 1/2 tablespoons cornstarch

1 teaspoon vanilla

2 to 3 pints raspberries, blackberries, blueberries, strawberries or a mixture

1/2 cup lime marmalade

1. For the crust, combine the flour, 2 tablespoons sugar, salt and lime zest in bowl. Cut the butter into half-inch slices and add to the flour mixture. Using your fingertips, a pastry blender or two knives, work the butter into the flour to make a fine crumbly mixture that starts to hold together. Sprinkle with 1 tablespoon cold water and toss until dough hangs together. Gather the dough into a ball, wrap it in plastic wrap and chill 30 minutes.

2. Unwrap the dough and press it evenly into the bottom and up the sides of a 9-inch tart pan with a removable bottom. (If the dough gets too soft to handle, return it in the pan to the refrigerator for about 5 minutes.) Place the dough-lined pan in the freezer for 30 minutes.

3. While the dough freezes, combine the milk, cream and 4 tablespoons sugar in a heavy saucepan. In a medium bowl, whisk the egg yolks with the remaining 2 tablespoons sugar and the cornstarch.

4. Bring the milk mixture just to a boil over medium heat. Ladle about one-third into the egg yolks and whisk until smooth, then beat the egg mixture into the milk mixture in the pan, whisking until it thickens and just comes to a boil, about 1 minute.

5. Remove from heat and stir in the vanilla. Transfer the mixture to a clean bowl and lay plastic wrap directly onto the surface. Chill until completely cold.

6. Heat the oven to 375 degrees. Bake the tart shell in the lower third of the oven until golden brown, 20 to 25 minutes. Cool completely on a rack.

7. Rinse the berries and hull if necessary. Pat completely dry.

8. Scrape the pastry cream into the cooled tart shell and smooth the surface. Carefully arrange berries on top, in alternating rings if using more than one variety.

9. Bring the lime marmalade to a simmer in a small saucepan and heat until melted. Brush lightly over the berries. Chill the tart at least 1 hour but no more than 4 before removing the ring from the pan and cutting the tart into wedges to serve.

Each serving: 463 calories; 5 grams protein; 63 grams carbohydrates; 3 grams fiber; 23 grams fat; 13 grams saturated fat; 144 mg. cholesterol; 78 mg. sodium.