If you haven't already, cook short-grain sushi rice (about 1 cup uncooked yields ~2 cups cooked). While warm, fold in rice vinegar and 1/4 tsp kosher salt; set aside to cool slightly so it's still warm but not steaming.

Make glaze (L&L-style BBQ-ish)

In a small bowl, whisk together 2 tbsp tamari (or soy sauce), 1 tbsp brown sugar, 1 tbsp water and 1 tsp sesame oil until sugar dissolves. Taste and adjust: it should be a savory-sweet glaze that will caramelize quickly.

Slice and pan-fry Spam

Open the spam can and remove block; slice into 8 even slices (about 1/4 inch thick). Heat 1 tbsp vegetable oil in a nonstick skillet over medium-high heat. Add spam slices in a single layer and fry 1–2 minutes per side until golden brown and crisped at the edges.

Glaze the Spam

Reduce heat to medium. Pour the prepared glaze into the pan with the spam and cook 30–60 seconds, spooning glaze over each slice, allowing it to caramelize and coat both sides. Remove slices to a plate and reserve any remaining glaze in the pan.

Assemble the musubi

Place a half nori sheet (shiny side down) on a work surface. Lightly oil a musubi mold or a clean rectangular measuring cup. Pack about 1/2 cup warm seasoned rice into the mold, press gently but firmly to form a compact layer. Place one glazed spam slice on top of the rice. Optionally sprinkle 1/2 tsp furikake or toasted sesame seeds over the spam for extra flavor. Top with another 1/4 cup rice and press down to compact. Slide the mold straight up to release the musubi.

Wrap the musubi

Brush a little of the reserved warm glaze (or water) along one short edge of the nori to act as glue. Wrap the nori around the rice-spam stack and overlap the edge. Press to seal. If the nori is stiff, briefly toast it over an open flame or in a dry pan for a few seconds to make it more pliable before wrapping.

Finish and serve

Let the musubi rest seam-side down for 1–2 minutes to set. Repeat with remaining ingredients to make up to 4 musubi. Slice in half if desired and serve warm or at room temperature. Store leftovers wrapped in plastic in the fridge for up to 24 hours; reheat briefly in a pan to crisp the nori and warm the rice.