How would I express a fraction?
The specific example you chose, recipes, are a bit idiomatic because they generally use arabic numerals {1 1\2}.
Use of fractions in roman text is a style issue and may change from guide to guide. The key potential difference is hyphenation.
[Using the Chicago Manual of Style]
One-and-a-half cups In this case, one-and-a-half operates as a compound adjective.
Some other examples: three-fourths, thirty percent loss, one hundred twenty-three and thirty-seven cents, I am one and a half, I am one-and-a-half years old
Time has a separate set of rules, but there is also overlap:
{I am three-and-a-half hours away},{I went on a three-hour cruise},{It is three thirty},{It is three twenty-seven},{It is three o'clock},{Four o'clock tea time},{Flight 897 arrives at three thirty},{half-hour ride will start in a half hour},{Both three am and three AM are acceptable, as are three a.m. and three A.M., but it's best to use arabic numerals at that point}.