Preheat oven to 375°F (190°C). Line a small baking sheet with parchment paper or foil.
Place salmon, skin side down (if it has skin) on the baking sheet. Spread with horseradish cream. Drizzle with a little oil. Sprinkle with salt & pepper. Bake for 15 to 18 minutes, depending on the thickness of the salmon, until salmon is just cooked & flakes easily with a fork. Flake the salmon into chunks; discarding the skin.
Melt the butter in a small frying pan over medium heat. Add leek & garlic. Cook, stirring occasionally for 5 minutes until leek is softened.
Roll one sheet of pastry on a lightly floured surface until you’re able to cut two, 5 3/4 to 6-inch pastry rounds from one sheet; discard pastry off-cuts. Cut out the pastry rounds & gently press them into two, greased 4 1/2-inch (11.5cm) tart pans with removeable bases. Repeat with the remaining pastry. Press the pastry around the side so it comes up just a little bit above the edge of each pan.
Whisk together eggs, cream, nutmeg & a pinch of salt in a medium bowl until well combined.
Divide leek, salmon, ricotta & dill between pans. Carefully pour cream mixture into each pan. Bake on the bottom rack of the oven for 40 to 45 minutes or until pastry is golden-brown & filling is set. Let stand for 10 minutes before serving. Serve warm or cold with lemon wedges, extra horseradish & dill sprigs. Makes 4.