1. Put water in a heavy pan, add sugar and leave on very low heat so that sugar may dissolve slowly_do not stir.
2. When sugar is completely dissolved bring to the boil, add cream of tartar and boil for 20-25 minutes to 115c (240F) on a candy thermometer-soft ball stage.
3. Put 1 3/4 cups of the ground almonds into a heatproof bowl and sprinkle half of the remaining almonds in the base of an 18 cm (7 inch) square cake pan.
4. Pour syrup onto almonds in bowl and leave until a skin begins to form around the edge, about 15 minutes.
5. Take a spatula and work it into the fondant in a figure-8 movement, continuing to work fondant until it begins to grain. Add vanilla essence during this process.
6. When mixture is cool enough to handle, knead into a ball.
7. Press fondant out flat on work surface and put onto almonds in prepared pan. Press into shape of pan. Sprinkle remaining almonds on top and press into fondant.
8. Leave until firm, about 3 hours, then cut into small diamonds(lozenges) with an oiled knife.
Tip : Makes about 45 pieces