Syntax for Mushroom Card Template

I'm trying to create a mushroom card stack which shows a toggle, yesterday's usage and today's usage. The part I'm stuck on is showing a card with today's usage.

I want two lines, the first line to show '123 kwh', the second line to show Today.

I have this:

- type: custom:mushroom-template-card

primary: {{states('sensor.tasmota1_energy_today') +' kwh' }}

secondary: Yesterday

icon: ''

entity: sensor.tasmota1_energy_today

layout: horizontal

fill_container: true

multiline_secondary: true

​

Which just renders a blank card, but this works:

- type: custom:mushroom-template-card

primary: a {{states('sensor.tasmota1_energy_today') +' kwh' }}

secondary: Yesterday

icon: ''

entity: sensor.tasmota1_energy_today

layout: horizontal

fill_container: true

multiline_secondary: true

It seems the value for "primary" needs delimiting somehow or it's just skipped over. The docs for the syntax seem... sparse.