Put flour, lard, margarine, and 1 cup water into large bowl and, using your hands, gently form mixture into a dough ball without mixing the fats into the flour. Transfer dough to a lightly floured surface and roll out into an 8" × 10" rectangle. Fold over short edges of dough into thirds, overlapping them, as if you were folding a letter. Rotate dough clockwise until long edges are parallel to you, then roll again into an 8" × 10" rectangle. Repeat folding, rotating, and rolling process 8 more times, lightly flouring work surface as necessary. Wrap dough in plastic and refrigerate for 2 hours.
Preheat oven to 400°. Divide dough into 4 equal pieces, shape into balls, and flatten each into a disk. Working with 1 disk at a time (rewrap and refrigerate remaining disks), roll out into a 9" round. Lay half of the round over the rolling pin. Place one-quarter of the rutabaga on flat half of dough and layer with one-quarter each of potatoes, onions, and beef; season generously with salt and pepper. Brush edge of dough with egg; fold dough over to form a half-moon shape. Pinch edges together to form a seam; pleat seam by folding and pinching dough over in small increments. Transfer pasty to an 8" × 12" piece of parchment paper. Repeat process to make 4 in all, placing them on indivdual pieces of parchment paper. Arrange the pasties on a baking sheet, pressing them against one another while pulling the edges of the paper up between them. Brush tops and sides of pasties with remaining egg.
Bake pasties until light golden, about 15 minutes. Spread the pasties on the baking sheet, reduce heat to 350°, and continue to bake until deep golden, about 50 minutes more. Set pasties aside and let cool to room temperature. Serve pasties with a cup of hot, sugary tea, if you like.