Brush your waffle iron with a little vegetable and pre-heat while you make the waffle batter.
Whisk together the soya milk and the vinegar. It may split but this isn't an issue.
Add the mashed potato to the soya milk / vinegar mix and whisk well.
In a separate bowl, whisk together the semolina, plain flour and baking powder. Season well.
Make a well in the middle of the dry ingredients then slowly add the milk / potato mixture, whisking well to make sure the batter is as smooth as possible.
Add just half of the chives (saving the rest as a garnish when you are ready to serve).
Spoon the batter into each section of the waffle iron (I use an ice cream scoop to do this). It doesn't matter if the mixture doesn't go all the way to the edge, it will expand slightly.
Cook the waffles for 4-5 minutes or until they are crisp and golden. Repeat with the remaining mixture until it has all been cooked.
To make the mushrooms
While you are batch cooking the waffles, add the mushrooms and butter to a small sauce pan.
Cook on a medium heat until the mushrooms are browned and cooked through.
Add the garlic to the pan and cook for 1-2 minutes then turn the heat to low until you're ready to serve.
To serve
Plate 1-2 waffles per person and top with the garlic mushrooms drizzling over any garlic butter that's left.
Place the saucepan back on a medium heat and wilt the spinach. Season the spinach and serve alongside the waffles and mushrooms.
Finally, add a spoon of creme fraiche to each plate and sprinkle with chives.