Spicy Shepherd's Pie with a Cheesy Leek Topping - Lavender and Lovage

Ingredients

• 400g to 500g Leftover roast lamb (roughly chopped, I used lamb left over from a Persian lamb roast)
• 300ml Leftover gravy (or 300ml fresh stock)
• Leftover cooked vegetables
• Leftover cooked rice
• 1/2 teaspoon ground cumin
• 1/2 teaspoon ground coriander
• 1 teaspoon smoked paprika
• 2 leeks, cleaned, trimmed and finely sliced
• butter, for frying
• 500g potatoes, peeled and cut into small pieces
• a little milk and butter
• 100g grated Cheddar cheese
• salt and pepper