What is a chicken and mushroom slice?
A chicken and mushroom slice is a British bakery item: a rectangular case of puff pastry filled with diced chicken and mushrooms in a thick, creamy white sauce. It is sold hot or cold in bakeries and supermarkets, eaten from the hand, and differs from a pie mainly in shape and portability.
By the chickenpie.net test kitchen · Published 14 August 2026
Anatomy of the slice
The slice is two rectangles of puff pastry sealed around a savoury filling, usually about 15cm long. The bottom layer stays fairly flat while the top puffs and flakes, and the filling is deliberately thick so it does not escape when eaten one-handed.
The filling is diced or shredded chicken and sliced mushrooms bound in a sauce closer to a paste than a pour: a heavily reduced white sauce or veloute, often seasoned with white pepper. That firmness is engineering, not stinginess, since a runny filling would make the slice impossible to eat while walking.
The slice earned its place through lunch logistics: it is baked in batches, holds well in a heated cabinet, and costs less than a plated pie. Supermarket chiller versions are made the same way and reheat acceptably at 180C (350F) for 15 minutes, though the pastry never fully recovers its first crispness.
Slice, pie, pasty: what is the difference?
The categories overlap, but shape and pastry usually settle it.
| Item | Pastry | Shape | Eaten with |
|---|---|---|---|
| Slice | Puff, two flat layers | Rectangle | Hands |
| Pie | Shortcrust or puff, in a dish or free-standing | Round | Knife and fork, usually |
| Pasty | Shortcrust, folded | Half-moon with a crimped seam | Hands |
| Bake | Puff, sealed oblong | Oblong with forked edges | Hands |
Making one at home
Roll ready-made puff to about 4mm, cut rectangles, and spoon a cold, very thick chicken and mushroom filling onto half of them, leaving a 2cm border. Top, seal the edges with a fork, egg wash, and cut two small steam slits.
Bake at 200C (400F) for 20 to 25 minutes until deep golden. The commonest home error is a filling that is too loose, so reduce the sauce further than looks reasonable and chill it firm before assembly.