Preheat the oven to 160C/325F/Gas mark 3
Cream the marg. with the sugar; beat in the syrup. Sift together the flour, carob and bicarb. Mix well, then work into the creamed mix to make a stiff dough. Knead, and roll out on a floured surface into an oblong strip about 13 x 23 cm/5 x 9 in. and 5 mm/ ¼ in. thick.
Cut in half to form two 6 cm/2 ½ inch wide rectangles. Place on the baking tray and bake for 15-20 minutes. Cut into equal-sized fingers while warm. Cool on a rack.
In a bowl, beat the butter until soft. Add the sugar, carob and coffee. Beat until smooth. Sandwich pairs of cooled fingers with the filling.