Walnuts have great fat content.
I found and selected the Idaho Carpathian Walnut, which flowers late, enabling it to produce even with a cold/late spring.
An important caveat about the entire species is that they produce Juglone in their root zone, and somewhat flowing downstream. This is poisonous to many other plants, and can ruin a design/garden if not taken into appropriate consideration. Juglone is a surefire tomato killer, whereas other effects can depend also on soil type, moisture etc., as to what is most severely affected. See the farmer's almanac] on the "dark side" of Walnuts.
All walnut species grow best on top quality sites. To be successful with Carpathian walnut, you need to choose a site with deep (three feet or more), well-drained loamy soils with pH values between 6.0 and 8.0. Smooth or gently rolling landscapes provide the best topography, although lower north- and east-facing slopes in mountainous terrain, as well as stream terraces and floodplains, also provide good sites for Carpathian walnut. Avoid frost pockets at all costs, as this species is very susceptible to frost damage. Poor site characteristics such as insufficient or excess moisture, steep slopes, south- or west-facing aspects, hardpan layers.