Spoon pizza sauce evenly into mushroom caps to cover bottoms. Top with mozzarella cheese and then pepperoni.
Pour water into the Instant Pot. Place stuffed mushrooms in steamer basket, then insert basket in pot. Lock lid.
Press the Manual or Pressure Cook button and adjust time to 2 minutes. Adjust pressure to Low. When timer beeps, quick-release pressure until float valve drops. Unlock lid.
Transfer mushrooms to a serving dish. Garnish with basil. Serve warm.
Notes
PER SERVING: CALORIES: 98 FAT: 6g PROTEIN: 7g SODIUM: 276mg FIBER: 1g CARBOHYDRATES: 5g NET CARBS: 4g SUGAR: 2g