Butter vs margarine
The answer depends on which margarine, and the number that decides it is on the packet.
The short answer
Margarine is a category and not a substance, so 'can I use margarine instead of butter' has no single answer. A hard baking margarine formulated near butter’s fat content behaves close to butter and substitutes well in most things. A soft spread carries substantially more water and less fat, and in shortcrust, rubbed-in mixtures and lamination that water is destructive — it hydrates the flour and develops gluten in methods whose entire purpose is to prevent that, so the pastry comes out tough for a reason the baker cannot see. What margarine never supplies is butter’s flavour and browning, which come from milk solids it does not contain. Where the fat is melted anyway and the flavour is carried by something else — a chocolate cake, many muffins — the swap is close to invisible. Where the fat is the flavour, it is not.
Where they differ
| Dimension | First | Second |
|---|---|---|
| Fat content | Around four-fifths, and consistent. | Varies enormously. This is the number that predicts the result. |
| Water content | Roughly a sixth. | Similar in a hard block; considerably more in a soft spread. |
| Plasticity | Plastic across a useful range. | Varies; some pastry margarines have a wider range than butter, spreads have almost none. |
| Creaming | Reliable when correctly softened. | Reliable from a hard block; poor from a soft spread. |
| Lamination | The reference. | Pastry margarines are formulated for it and some outperform butter for handling. |
| Flavour | Milk solids and dairy notes. | Little, and no amount of formulation adds it. |
| Browning | Milk solids brown. | Browns less. |
Differences that do not matter
These are real distinctions that are unlikely to change your decision. They are listed so you can stop thinking about them rather than left out so the comparison looks decisive.
- Shortening the crumb. Yes. Yes — a fat is a fat for this purpose.
The claim BakeHQ will not make
Comparisons of these two are unusually prone to becoming arguments about something else. Both a health argument and a craft argument attach themselves to the question, and neither is answered by how a fat behaves in a mixture.\n\nBakeHQ describes what each does to a bake and stops there. It makes no health claim in either direction, and it does not rank them. The useful finding is the one the packet already tells you: fat content predicts behaviour, and a hard block and a soft spread differ from each other more than butter differs from a hard block.