To prepare filling, heat up oil and butter in a sautéing pan. Pan sauté onions and garlic until translucent and aromatic.
For the pastry, combine dry ingredients in a bowl. Cut in the shortening until mixture becomes mealy. Add cold water until it forms a ball of dough. Set aside to rest.
To assemble, roll out the dough to ¼ inch thickness. Cut into rounds using a large cookie cutter. Fill a round with 1-2 tablespoons filling. Then top with another round of dough. Seal the edges by brushing it with egg wash then pinching with a fork.
Bake in a preheated 350°F/177°C oven for 20-25 minutes until the top is golden brown. Brush top with egg wash after 10 to 15 minutes, then continue baking until pastry domes all are golden brown and cooked.