• Preheat the oven: Preheat your oven to 180°C.
  
• Cut in the butter: Freeze the 250 grams butter, cold (or margarine) beforehand, then grate it into a bowl with the 500 grams flour, 0.5 teaspoons cream of tartar, and 0.3 teaspoons salt.

  Rub together with your fingertips until it looks like coarse crumbs.
• Bring the dough together: Add the 1 cups soda water, chilled a little at a time, mixing gently with a knife until the dough just comes together.
• Rest the dough: Shape the dough into a ball, cover with a cold, damp cloth, and chill in the fridge.
• Cut and fill: On a floured surface, roll the dough out (not too thin) and cut circles with a cookie cutter. Re-roll scraps and keep the cut dough chilled between batches. Spoon a small amount of 1 cups smooth apricot jam into the center of each circle.
• Seal the tarts / tertjies: Brush half the rim of each circle with 1 egg, beaten (for sealing edges). Fold over into a half-moon and press the edges with a fork, or prick with a toothpick, to seal and prevent the jam from leaking out during baking.
• Bake until golden: Bake in the preheated oven until lightly golden brown.

Notes

• Makes roughly 5 dozen tarts / tertjies, depending on cutter size. Sealing well with a fork and pricking with a toothpick helps stop the jam from bubbling out during baking. These freeze beautifully unbaked — just bake straight from frozen, adding a few extra minutes.