Bring a pan of water to the boil and lower in 8 of the eggs. Bring back to the boil and simmer for 6 mins. Drain, then cool under cold water. Peel carefully as the yolks will still be quite soft. Meanwhile, mix the sausagemeat and onions together using your hands.
Roll out a block of pastry until large enough to cut 3 x 18cm circles (this is about the size of a large cereal bowl or a side plate). Re-roll the trimmings; you should get 4 circles from each block. Have 2 baking sheets ready, dusted with a little flour.
Using slightly wet hands, squash out an eighth of the sausage mix over each of the rounds of pastry, going almost right to the edges. Slightly wet the edges of the pastry. Sit a peeled egg in the middle of the sausage, grind over a little salt and pepper, then pull the sides up over the egg and seal. Crimp the edges and put onto the baking sheet.
Beat the final egg and brush over the pasties. Chill for 30 mins. Heat oven to 220C/200C fan/gas 7. Bake the pasties, one tray at a time, for 25 mins until golden. Bake them on the morning of the picnic and take them along warm, or bake them the day before, allow to cool, chill in the fridge, then pack up for your picnic with your sauce of choice.