The dough can be prepared in advance, and it's best to use your hands to knead. In a large bowl, mix the 2 tablespoons of vegetable oil into the flour until you can no longer see or feel the oil. Mix the salt into the warm water, and pour the water gradually into the dough, kneading with your hands. Once the dough is kneaded well, set aside in a plastic bag or plastic wrap for 20 minutes, then knead again.
While the dough is resting for 20 minutes, you can work on the filling! In a saucepan, warm the oil. Once it's hot fry the cumin seeds, cumin, turmeric and ginger for 30 seconds.
Add the potatoes, squash and cauliflower, and simmer on a low heat for 15 minutes. Add a few drops of water if the vegetables stick to the pan.
Once cool, add the peas and corn, salt to taste. You can also add a spoonful or two of fresh cilantro.
Assembling the samosas: Roll the samosa dough into 4-5 inch circles, and cut the circle in half with a knife. Using a bit of water, take your semicircle and make a fold in the shape of a triangle. Seal along the fold.
Put this cone carefully between your thumb and index finger and place a ball of the filling inside. Wet your finger and run it along the edges of the dough with water and seal to enclose the stuffing, pinching the edges and folding over.
Once the samosas are assembled, cook at 350 Fahrenheit for 10 minutes on one side, then flip over and cook for 10 minutes on the other side.
This recipe makes about 20 samosas.