Pizzetta Bianco with Alaska Smoked Salmon, Herb Crème Fraîche

Ingredients

• 200g crème fraîche
• 2 tbsp hot horseradish sauce
• 1 tbsp lemon juice
• Grated zest of 1 lemon
• 2 tbsp chopped fresh dill, plus small sprigs for garnish
• 2 tbsp chopped fresh chives
• Sea salt flakes
• Freshly ground black pepper
• 1 large red onion, thinly sliced
• 1 tbsp olive oil, plus more for brushing
• 250g ciabatta bread mix
• Plain flour, for dusting
• A handful of rocket
• 200g thinly sliced Alaska smoked salmon, torn into small pieces
• 1 x 100g jar Alaska keta salmon roe