I can't seem to succeed in creating a large button with a large icon in it.
This creates a large button, but the icon inside is small:
<Button className="pt-large" iconName="circle-arrow-left"/>
This forces the icon to be big, but creates extra space to the left of it (i.e., the button is not square any more).
<Button className="pt-large">
<Icon iconName="circle-arrow-left" iconSize={20}/>
</Button>
Answered on GitHub, this is by design. The design system uses regular icons in large buttons. See https://github.com/palantir/blueprint/issues/2013.