I trying to find out what I could use to substitute "Baking spread"? It is in a British recipe and in the US, where I live, I've never seen this.
"Baking Spread" is what used to be Margarine, before most of the ingredients of margarine were banned [predominantly the hydrogenated vegetable oils & trans fats].
Vegetable oils in varying proportions (70%)(rapeseed, palm, sunflower), water, salt (1.5%), buttermilk, preservative ( potassium sorbate), emulsifier (mono- diglycerides of fatty acids), citric acid, flavourings, vitamin A and D, colour (carotenes).
Not all vegan butter is ideal for baking. Most dairy-free spreads are similar to margarine in texture and tend to contain more moisture than traditional butter. Look for a product called baking block (or baking fat) on the supermarket shelves. It’s vegan and behaves like butter – it even works beautifully in laminated pastry doughs such as croissants and pain au chocolats.
That said, I've had reasonable luck baking with a "vegan butter" called Melt which is readily available in the US (at least in the Pacific NW).
Many "spreads" in the U.S. contain more water than traditional butter or margarine, which is what makes them easier to spread. However, I compared the fat content of Flora, a popular baking spread brand in the UK, with that of Earth Balance Buttery Sticks in the U.S., and they are the same (79%) so that seems like a suitable substitution. For non-baking use I like Smart Balance, but it only has 64% fat content so it doesn't act the same in all applications as higher fat butter or margarine.
Although Smart Balance is available in stick form with the same fat level and advertises itself as being good for baking, I wouldn't use it in British baking recipes calling for baking spread unless I add a bit of extra oil to the recipe and slightly reduced the amount of other liquid.
When shopping in the U.S., look carefully at the product packages to see what the fat content is (this doesn't seem to be required and not all brands/products show it). But Earth Balance is widely available in the U.S. and seems to be a one-to-one substitution for British baking spread.