Mix together pineapple and chili sauce and set aside until needed.
Lightly toast the bread slices and cut off the crusts.
Place the shrimp, cilantro, scallions, ginger, fish sauce, sugar, and egg white in a food processor and pulse until the mixture forms a rough paste. Season to taste with salt and white pepper.
Spread an even layer of shrimp paste on each slice of bread and sprinkle with sesame seeds, pressing lightly to adhere.
Melt 2 Tbs. butter in a large non-stick skillet and fry the bread in batches, shrimp-side down, about 2 minutes, or until the shrimp is cooked through. Flip toasts and saute briefly, about 1 minute, to crisp the other side. Add additional butter to the skillet as needed.
Divide the greens between 2 slices of toast and top with remaining toasts. Cut sandwiches in half diagonally and serve with pineapple dipping sauce.