Heat combined olive oils in medium-large saucepan. Add potato and broccoli. Cook over medium-high heat for 5-10 minutes.Meanwhile, dissolve stock cubes in boiled water.Add stock, stir to combine. Bring to boil, then reduce to a simmer. Simmer, covered, for 25 minutes. Add in spinach, simmer for further 2 minutes.Remove from heat and cool for 5 minutes. Blend with stick-blender until smooth.Season with salt and pepper, to taste.Serve with a dollop of lactose-free natural yoghurt, if desired.