Spanakopita Triangles + Then Some

Melt one tablespoon butter in a large heavy skillet over moderate heat, add onions and garlic and saute for a minute, then cook spinach, stirring, until wilted and tender, an additional 4 to 8 minutes (less for baby spinach, more for grown-up spinach). Remove from heat and cool, about 10 minutes. Press mixture in mesh colander (or wring in cheesecloth) to remove as much liquid as possible, then coarsely chop. Transfer to a bowl and stir in feta and lemon juice. Season with salt and pepper to taste. Let filling cool and follow instructions for phyllo triangles.

Place the dried mushrooms in a small bowl and add the boiling water. Let stand for 30 minutes until softened. Drain and mince the mushrooms. In a large saute pan over medium heat, melt the butter. Add the green onions and saute, stirring occasionally, until soft, about five minutes. Add the garlic, rosemary and thyme and continue to cook, stirring, for one minute more. Increase the heat to high, add the fresh and rehydrated mushrooms, and saute until the mushrooms are tender and the liquid they released has completely evaporated, six to eight minutes. Transfer to a plate and let cool, then stir in blue cheese, adjust seasoning to taste, and follow directions for phyllo triangles.

Heat oil in a 12-inch heavy skillet over medium-high heat until it shimmers, then sauté fennel seeds until a shade darker, about 30 seconds. Stir in onions, teaspoon salt, and pepper, then reduce heat to medium-low. Cook, stirring occasionally, until onions are very tender and lightly golden brown, about 20 to 30 minutes. Let onions cool. Stir in mustard and goat cheese and follow instructions for phyllo triangles.

Preheat oven to 375°F. Melt butter in a small saucepan, then cool. Cover phyllo stack with 2 overlapping sheets of plastic wrap and then a dampened kitchen towel.

Take one phyllo sheet from stack and arrange on a work surface with a long side nearest you (keeping remaining sheets covered) and brush with some butter. Top with another phyllo sheet and brush with more butter. Cut buttered phyllo stack crosswise into 6 (roughly 12- by 2 3/4-inch) strips.

Put a heaping teaspoon of filling near one corner of a strip on end nearest you, then fold corner of phyllo over to enclose filling and form a triangle. Continue folding strip (like a flag), maintaining triangle shape. Put triangle, seam side down, on a large baking sheet and brush top with butter. Make more triangles in same manner, using all of phyllo.

Bake triangles in middle of oven until golden brown, 20 to 25 minutes, then transfer to a rack to cool slightly.

Pastry triangles can be formed, but not baked, three days ahead. Arrange in one layer in heavy-duty sealed plastic bags, then freeze. Bake frozen pastries (do not thaw) in same manner as above.