Smoked mackerel & horseradish on baked beetroot rostis

A fresh twist on a classic smoked mackerel recipe, these beetroot canapés make a great nibble with an aperitif. Rostis are perfect party food

2 large beetroot (about 300g), peeled, ends trimmed and spiralized into thin noodles
2 medium Maris Piper potatoes (about 300g), peeled, ends trimmed and spiralized into thin noodles
1 ½ tbsp olive oil
150g smoked mackerel, skin removed and broken into 20 large flakes
handful of chives, finely chopped
150ml crème fraîche
1 tbsp hot horseradish sauce
zest and juice of ½ lemon

Heat oven to 200C/180C fan/gas 6.Line two baking trays with baking parchment. Pat the spiralized vegetables dry with kitchen paper and cut any long spirals into shorter noodle lengths then tip into a large bowl with the olive oil and season with salt and pepper.
With your hands, shape the mixture into 20 small circles. Space out between the two baking trays, making sure there is enough space for each rosti to cook evenly. Bake for 20 mins or until firm and crisping at the edges, carefully flipping the rostis after 10 mins.
While the rostis are roasting, mix together the crème fraîche, horseradish, lemon zest and juice and a generous grind of black pepper together in a small bowl.
Top each rosti with a spoonful of horseradish crème fraîche, a piece of smoked mackerel and some chopped chives.