Sift the buckwheat flour, salt and baking powder into a bowl. Make a well in the centre. Beat the egg and buttermilk together in a separate bowl, then pour into the well and whisk into the dry ingredients until bubbles appear on the surface and the batter is smooth and runny.
Pour the pancake mixture into a jug, cover with plastic wrap and set aside for 20 minutes while you make the rhubarb topping.
Trim and wash the rhubarb stalks then cut into 2.5cm (1 in) pieces. Place the rhubarb, pear concentrate, ginger and water in a heavy-based pan, cover with a tight-fitting lid and place over a low to medium heat.
Test the rhubarb after 5 minutes and continue to check every 2 minutes therafter until it is soft and tender.
Set aside to cool slightly while you ccok the pancakes.
Grease a small pancake pan with the oil and wipe off the excess with a paper towel. Place the pan over a medium heat and, when hot, pour in sufficient mixture to make a pancake about 2mm (1/16 in) thick. The pancake is ready to turn once you see little air holes appearing on the uncooked surface. Flip the pancake and cook uuntil golden, then repeat the process until the batter mixture is finished.
Stack the cooked pancakes on a plate and keep warm in a slow oven (150 degrees Celsius) as you cook the rest.
To serve, spoon the rhubarb topping over the pancakes and top with sheep's yoghurt.
The rhubarb topping will keep in the fridge in a covered container for about 4 days.