Adding content for the sake of adding content has long been a bad idea. When someone comes to your website looking for a recipe, don't go on a 5-paragraph rant about your weekend and mother in law visiting.
But adding topically relevant content that is unique to that page is a great way to provide value to your readers, while lengthening your content so that it ranks for a broader range of keywords.
Let's take the humble apple.
Ma's Apple Pie
You're writing an apple pie recipe for your readers.
What kind of apples are you using?
This seems like a dumb question at first - apples are only a single ingredient in the entire recipe. But there's a huge range of different apples, and different apples may be better suited for different recipes.
Someone using a (bland) red delicious apple is going to need different amounts of sugar than someone using a (sweet) empire apple. But this isn't obvious to your readers, who don't have your level of background knowledge and baking experience.
Assume your readers need to be hand-held, and break everything down as much as possible.
Another great way to fill out content while helping the reader is to provide substitutions for ingredients. Maybe instead of using a different type of apple than you use, a pear might be a better ingredient to substitute.
Here, the varietal is going to make a big difference as well: