Cut chicken and grouse into serving pieces, and marinate for 2 days in red wine. Drain and dry pieces well. Sprinkle pieces generously with flour.
Dice bacon and blanch it by placing it in cold water and bringing it slowly to a boil. Drain. Sauté bacon in butter until golden; remove bacon and sauté chicken and grouse pieces in remaining fat until golden. Pour over the juices of the marinade; add bacon bits, salt, freshly ground black pepper, and crumbled rosemary and thyme.
Blanch onions in boiling water for 10 minutes; drain and add to casserole. Bring to a boil; reduce heat and simmer for 1½ hours, uncovered. If the sauce reduces too much, add more wine or a little boiling water. Cool.
Sauté sausages in olive oil. Shell eggs and slice in quarters. Arrange pieces of chicken and grouse in a large deep pie dish around a pie chimney; top with sausages and quartered hard-boiled eggs, and pour in sauce, together with onions and bacon bits. Cover with flaky pastry; brush with beaten egg yolk and