Add beetroots, potatoes, and stock into a saucepan
Bring to a boil on medium-high heat
Simmer for 25 minutes on low-medium heat until the vegetables are soft
Remove from the heat and let cool.

Fit the Blender attachment
Add the contents of the saucepan into the Blender 
Select the Blend preset
Chill in the fridge for 1 hour
Ladle the soup into serving bowls
Garnish with yoghurt, cucumber, and feta.

Serve.