Sift flour and salt into a bowl.

Add oil and water, mix to form a firm dough.

Knead the dough for 5 minutes.

Let the dough rest for 30 minutes covered in an oiled bowl.

Boil, steam, or microwave the sweet potato until tender.

Drain the sweet potato.

Place spinach in a bowl and cover with boiling water for 2 minutes.

Drain spinach, rinse with cold water, and squeeze out excess water.

Chop the spinach.

Melt ghee in a skillet over medium heat.

Add onion and garlic, sauté for 5 minutes.

Add cumin and mustard seeds, sauté for 30 seconds.

Add sweet potato and spinach, sauté for 2 minutes.

Divide dough into 12 balls.

Roll each ball into a 6-inch round and cut in half.

Place a tablespoon of filling in the center of each half-moon.

Brush edges with water and fold dough over the filling.

Repeat with remaining dough and filling.

Heat oil in a saucepan to medium heat.

Deep-fry samosas, 4 at a time, for 3 minutes or until browned.

Transfer samosas to paper towels.

Serve with yogurt.