In a small Mixing Bowl, whisk together the 3 tbsp aceite de oliva, 2 tbsp vinagre balsámico, 1 tbsp salsa de soya, 3 dientes de ajo picados, 1 tsp hojas de tomillo fresco, 1 tsp mostaza Dijon, ½ tsp pimienta negra recién molida, and ¼ tsp sal kosher until well combined.

Gently wipe the 4 sombreros grandes de champiñón portobello tallos removidos, branquias limpias si se desea caps clean with a damp paper towel. Remove the stems. If you prefer a less intense, less watery result, use a spoon to scrape out the dark gills on the underside of each cap — this is optional but recommended.

Place the 4 sombreros grandes de champiñón portobello tallos removidos, branquias limpias si se desea caps in a large Ziploc Bag or a shallow dish. Pour the marinade over them, turning to coat all sides. Seal and let marinate at room temperature for 15–20 minutes (or up to 1 hour in the fridge).

Preheat your Grill to medium-high heat, about 400–450°F. Clean and lightly oil the grates.

Remove the 4 sombreros grandes de champiñón portobello tallos removidos, branquias limpias si se desea from the marinade, letting any excess drip off. Reserve the remaining marinade for basting.

Place the 4 sombreros grandes de champiñón portobello tallos removidos, branquias limpias si se desea caps gill-side down on the hot Grill. Cook for 4–5 minutes until grill marks form and the caps release easily from the grates. Baste the top (stem side) with the reserved marinade.

Flip the 4 sombreros grandes de champiñón portobello tallos removidos, branquias limpias si se desea so they are gill-side up. Baste again with the remaining marinade. Grill for another 4–5 minutes until the 4 sombreros grandes de champiñón portobello tallos removidos, branquias limpias si se desea are tender all the way through and juicy. They should look deeply browned and slightly collapsed.

Transfer to a serving plate. Squeeze a little fresh 1 tbsp jugo de limón recién exprimido over each cap and scatter with fresh 2 tbsp perejil fresco picado grueso. Serve immediately.