Dough: In a medium bowl, mix flour, salt and butter until the mixture resembles fine bread crumbs. Pour in water, using more (up to 1/4 cup) if necessary to make a smooth dough. Pat into a ball, place on a lightly floured surface and knead for 10 minutes, or until dough is smooth and elastic. Return to the bowl, cover and set aside.
Heat oil in a large, deep frying pan to 190 degrees C.
Filling: Melt butter in a medium saucepan over medium-high heat. Stir in onion, garlic, chilli and ginger. Cook for 5 minutes, or until onions are golden brown. Stir in turmeric, chilli powder, lamb and salt and cook until the meat is evenly brown, about 10 minutes. Stir in garam masala and lemon juice. Continue cooking for 5 minutes, then remove from heat.
Divide dough into 15 equal portions. Roll portions into balls, then flatten into 10cm circles. Cut each circle in half. Dampen edges and form semicircles into cones. Fill cones with equal portions of the lamb mixture. Dampen top and bottom edges of cones, and pinch to seal.
Carefully lower cones into preheated oil a few at a time. Fry until golden brown, 2 to 3 minutes. Drain on paper towels. Serve warm.