In a large pot over medium heat, add coconut oil and finely minced shallots, and fry until the shallots are golden browned. Add yellow and red curry paste and curry powder, then cook for another 2 min until fragrant. Add coconut milk, chicken stock, lemongrass, lime leaves, dark brown sugar, peanut butter, paprika and freshly ground black peppers.
Keep on a simmer while stirring occasionally. It's ready when you see red fat starting to separate from the sauce (which is what we want), about 40~50 min. Can be made the day before.
Roast the salmon fillets in a pan until skin is crispy and golden brown all over but still pink in the centre, place on top of the curry sauce and scatter with a little ricotta. Serve with rice.