Place the trout in a heatproof plate, cover it with a piece of plastic wrap, and steam it in the microwave on high for 7-10 minutes (depending on the wattage of your microwave oven) or until the fish is completely cooked through and flakes easily when tested with a fork. Allow the fish to cool.
Once the fish is cool enough to handle, peel off the skin, separate out the meat (you should up with about 180g of cooked fish meat), pick off and discard any big bones, and place the meat in a food processor (a mini-chopper or a mortar would be fine as well). Pulse the fish until the flakes are fine.
Transfer the fish flakes to a dry skillet set over medium-low heat. Slowly toast the fish, stirring constantly, until the flakes go from off-white to deep golden brown. This could take up to 30 minutes, depending on the surface area of the skillet (wider means better moisture evaporation). You want the fish flakes to dry completely, so don’t rush this process by increasing the heat in hopes of shortening the cooking time.
Once the fish is done, remove the skillet from heat. Stir the sugar and salt into it off the heat and set aside. (We don’t want the sugar to be entirely melted; we want a bit of it to melt and coat the warm fish flakes while the majority remains intact.)
Add the oil and the sliced shallots to another small skillet when the skillet is cold, then set it on medium heat. Stir the shallot pieces around constantly to make sure they’re cooked and browned up evenly.
Once the shallots are crispy, turn off the heat and immediately transfer the mixture to a heatproof bowl to prevent the residual heat in the pan to cook the shallots further and turn them too dark.
Let the shallots cool down, then stir them into the fish mixture along with about a tablespoon of the oil in which the shallots were cooked.
Serve the dip with fresh watermelon chunks.
The completely cooled dip can be stored for up to 2 weeks in an airtight container at room temperature. To use, it’s best to scoop out just the amount you need with a clean spoon. That way, the dip stays fresh longer.