Preheat the oven to 350°F. Sprinkle the cumin seeds onto a dry baking tray. Once the oven is at temperature, put the tray into the oven and bake for 5-7 minutes. Remove from the oven and set aside to cool (about 10 minutes). Once cooled, grind the seeds into a fine powder. Alternatively, you can achieve the same result by toasting your seeds on a dry skillet on medium-high heat for about the same amount of time.
Sprinkle the pistachios, sesame seeds, coriander seeds, and walnuts onto a dry baking tray. Once the oven is at temperature, put the tray into the oven and bake for 5-7 minutes. Remove from the oven and set aside to cool (about 10 minutes).
Transfer the toasted nuts and seeds to a food processor along with the brown sugar, thyme, cinnamon, and ground pepper. Pulse until the dukkah has reached your desired consistency (I like it to be somewhat finer, but it's quite nice with bigger chunks as well).
Transfer the dukkah mixture to a bowl and add the maldon salt and toss to combine.
In a medium to large saucepan, cover the sweet potato chunks with cold water. Season the water (I use about a handful of kosher salt), and bring to a boil.
Cook until tender enough to pierce easily with the tip of a knife (about 15-20 minutes). When they're done cooking, the sweet potato will fall easily off the knife.
Drain the sweet potatoes, then mash them. Add the cream, butter, and ground cumin and stir to combine. Add salt to taste (taste before adding salt, because it may not need any since the potatoes were seasoned in the water).
Transfer to a serving plate or bowl and garnish liberally with dukkah, concentrating the majority of the dukkah to the center so that you can see the beautiful color of the mashed sweet potato on the edges of the plate.