Combine flour, yeast, sugar, spices and currants in a large bowl. Make a well in the center.
Combine milk and spread in a small saucepan over medium heat and stir until melted. Mix egg replacer with 2 tbs water until smooth. Add to milk mixture and stir into flour mixture until combined.
Turn out onto a floured surface and knead for 5 minutes or until smooth. Lightly coat dough with flour and place into a clean, dry bowl. Cover with plastic and set aside in a warm place for 30 minutes or until doubled in size.
Punch dough down to its original size. Knead for 1 minute on a lightly floured surface until smooth. Divide into 12 even pieces and shape each into a ball. Place balls onto a roasting pan lined with baking paper, spaced 1cm apart. Cover with plastic and set aside in a warm, draught-free place for 30 minutes or until risen. Preheat oven to 190°c.
Meanwhile, for flour paste, combine flour, icing sugar, vanilla and 1/3 cup water in a small bowl and stir until smooth, adding a little more water if too thick. Spoon into a small snap-lock bag and snip off one corner. Remove plastic from buns and pipe crosses on top. Bake for 20-25 minutes or until buns are cooked through. Brush buns with jam and serve warm.