Step 1

Combine the flour and salt in a mixing bowl. Cut in half of the chilled butter with a pastry blender until the butter/flour mixture resembles granola. Work quickly to keep the butter as cold as possible., Dice the remaining butter and add to the butter/flour mixture in the bowl. Work in the new butter until it is the size of dried cranberries. You can flatten the pieces slightly with your fingers as you go along, creating leaves of butter coated in flour., Sprinkle about half of the ice water over the butter/flour and work gently, adding more water as needed until the dough forms a rough mass. Knead the dough for about 30 seconds., Divide the dough in half and press gently into 2 discs. You should still be able to see bits of butter in the dough. Wrap each disc in plastic wrap and refrigerate for 30 minutes. You can keep the dough in the fridge up to overnight if desired., While the dough is chilling, prepare the filling. Melt the butter in a medium-sized saute pan. Add the onions and garlic, cooking for two to 3 minutes until the onions turn translucent. Take care not to burn the garlic., Add the curry powder and cumin and saute for an additional minute. Add the potatoes and turn to coat well in the spices. Cook and break up the potatoes for a few more minutes. You can mash the filling smooth at this time, or leave pieces of potato according to your preference., Taste the filling for seasoning; adjust with salt, pepper, and hot sauce, if desired. Remove from the heat and stir in the peas., Allow the filling to cool to just barely warm. When you're ready to roll your dough, preheat the oven to 400°F and lightly grease two baking sheets, or line them with parchment., Working with one disc at a time, roll the chilled dough 1/8" thick. Cut circles of dough with a sharp-edged round 3" cutter. Place a generous teaspoon of filling onto each round; a level teaspoon scoop works well here. Fold into half-moons and gently squeeze edges together; then press edges with a fork to completely seal., Fold into half-moons and gently squeeze edges together; then press edges with a fork to completely seal. Place on the baking sheets and brush with the beaten egg to coat., If desired, refrigerate samosas for 30 minutes or so, to chill the crust; this will result in flakier pastry., Bake the samosas for 20 to 30 minutes, or until deep golden brown. Serve hot with yogurt or sour cream (or even better, mango chutney) for dipping.

Step 2

, Store leftovers, well wrapped, in the refrigerator for several days; freeze for longer storage.