Cut one cauliflower into small pieces.

Place the cauliflower pieces in a food processor and process until it resembles a rice-like texture. This creates cauliflower rice. Alternatively, you can use frozen cauliflower rice. If using frozen cauliflower rice, cook it directly.

Place a large nonstick frying pan over medium-high heat and add the butter and the riced cauliflower. Cook for 7-10 minutes until the cauliflower is tender (slightly yellowish). Remove from the heat.

Add the sweetener and the vinegar to the cooked rice. Adjust the amounts if desired and let it cool down in the fridge (approximately 15-20 minutes).

Cut the cucumber into 10 short slices or 5 long slices.

Place a sushi nori sheet onto a sushi mat, shiny side down, and top with a fifth of the cooled cauliflower rice mix.

Spread the rice evenly onto the sheet, leaving a 1/2-inch gap at one end.

Add a fifth of your chosen filling ingredients (2 short cucumber sticks, 2 crab sticks, and 2 cream cheese sticks) and roll firmly until you reach the edge of the rice. Sprinkle some water on the end of the sheet, and finish rolling. Use the sushi mat to firm up the roll.