Butter has a lower melting point than does lard or shortening. Butter, as has already been mentioned, contains milk solids, and water. For things like pie crust, lard is a natural choice that produces a superior product. Also, it has less cholesterol than butter.
What happens with butter in a pie crust is that after it is added to the flour, if the flour is worked too much, the gluten can develop as the water reacts with the wheat protein. Also, when the crust begins to cook, the butter will melt before the dough starts to set into a solid, resulting in the top of the crust sides collapsing toward the pie center. I found that out the hard way.
Some cookies are meant to spread out into a gooey, flat cookie, such as Nestle's Toll House cookie. Other, more cake-like cookies can benefit from butter's rich favor, such as shortbread or shortbread cookies.
The only problem I have with lard is that it's hard to find in pure form.
Butter and lard are the go to fats in my house, and olive oil. I hope this helps.
Seeeeeya; Chief Longwind of the North
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