In a medium bowl, dissolve the yeast in the water. Add the flour and salt and stir well. Let stand, loosely covered, to ferment for 45 minutes.
Meanwhile, prepare the filling: Mix the ingredients in a bowl until you have a homogeneous mass. Set aside.
When ready to proceed, heat a small heavy skillet over medium heat for 5 minutes. Lightly brush the skillet with butter. Stir the batter well to blend. Scoop up about 2 1/2 Tablespoons batter and pour onto the skillet to make a 4-inch round or an oval about 4 inches long. Cook until bubbles appear on the top and the top has a matte dull surface, about 1 minute and 20 seconds. The underside will be just touched with the palest brown. Transfer to a plate cooked side down.
Scoop up 1 teaspoon filling and squeeze it in your hand into a firm oblong, then place it on the cooked pancake. Immediately fold the pancake over and pinch the edges together to make a sealed half moon shape. (The trick with atayef is to fill them while the top of the pancake is still warm so the edges stick together well.) Set aside on a plate, and repeat with the remaining batter and filling. (Once you get comfortable with the sequence of steps, you may want to have two skillets going at once, to speed production. But even with only one person and one skillet, you can get all the atayef made in a short time.).
The filled pancakes can sit, loosely covered, for up to 3 hours before being fried.
When ready to proceed, pour about 1 inch of peanut or vegetable oil into a deep fryer or stable wok or other deep frying arrangement, and heat to 375°F Use a thermometer to check, or the following test: Stick a chopstick vertically into the hot oil. If bubbles come rising up beside it, the oil is hot enough. Have a slotted spoon by your stove top as well as two paper towel-lined plates.
Slide the first half moon into the hot oil. It should bubble a little. Then slide in another, and another. Each should cook for about 30 seconds, until lightly browned; turn each over in the oil after about 15 seconds. With the slotted spoon, transfer to a paper towel-lined plate. Fry the remaining half moons in the same manner. Serve hot or warm, with tea or coffee. Makes 12 to 15 half moon shaped pancakes.
NOTE: Kanefa and haloumi, is available in specialty stores and great for stuffing pancakes. Ricotta salata is like feta, however, and is made from fresh ricotta that has been salted and dried. It is available in supermarkets.