Unfold pastry sheet; lay flat on a lightly floured board. Roll into a 1/16-inch-thick rectangle (10 by 14 in.); cut in half crosswise. Lightly brush both halves with egg. Sprinkle one evenly with seasoning mix. Set remaining half, egg side down, over seasoned half, aligning edges. Gently roll to seal layers without enlarging rectangle.
Cut rectangle lengthwise into 1/2-inch-wide strips. Brush tops lightly with more egg; save remaining egg for other uses or discard. Sprinkle strips evenly with salt (or sugar if using a sweet seasoning mix); with your hand, press lightly into surface of puff pastry.
One at a time, pick up strips by both ends, twist in opposite directions, and transfer to buttered 12- by 15-inch baking sheets (you'll need two), placing strips about 1 1/2 inches apart. Press ends onto sheets.
Bake salt-crusted straws in a 400° regular or convection oven (sugar-crusted ones at 350°) until crisp and lightly browned, 8 to 13 minutes (14 to 20 minutes for sweet), switching pan positions halfway through baking. Let straws cool about 1 minute on sheets, then, with a wide spatula, loosen while still warm and transfer to rack (if straws stick, return pans briefly to oven to reheat). Serve warm or cool.
Mexican Cheese Seasoning Mix: In a small bowl, mix 1/2 cup finely shredded Mexican cheese blend or cheddar cheese, 2 teaspoons cumin seeds, and 1 teaspoon chili powder.
Per straw: 119 cal., 64% (76 cal.) from fat; 6 g protein; 4 g fat (9 g sat.); 1 g carbo (4 g fiber); 237 mg sodium; 17 mg chol.
Tomato-Basil Seasoning Mix: In a small bowl, mix 1/4 cup grated parmesan cheese, 2 tablespoons finely chopped drained dried tomatoes in oil, 1 tablespoon minced garlic, and 1 teaspoon dried basil.
Per straw: 114 cal., 61% (69 cal.) from fat; 5 g protein; 7 g fat (3 g sat.); 8 g carbo (4 g fiber); 241 mg sodium; 15 mg chol.
Cinnamon-Nut Seasoning Mix: In a small bowl, mix 1/3 cup finely chopped pecans, 1 tablespoon firmly packed brown sugar, and 1/2 teaspoon ground cinnamon.
Per straw: 126 cal., 62% (78 cal.) from fat; 9 g protein; 7 g fat (2 g sat.); 10 g carbo (4 g fiber); 48 mg sodium; 14 mg chol.
Coconut-Orange Seasoning Mix: In a small bowl, mix 1/3 cup sweetened flaked or shredded dried coconut, 1 teaspoon sugar, 1 teaspoon grated orange peel, and 1/2 teaspoon ground ginger.
Per straw: 115 cal., 59% (68 cal.) from fat; 7 g protein; 6 g fat (5 g sat.); 10 g carbo (4 g fiber); 52 mg sodium; 14 mg chol.