Teriyaki Mushroom Sushi Burrito

Name: Teriyaki Mushroom Sushi Burrito
Ingredients: 1 cup uncooked sushi rice; 1 cup water; 1 tbsp rice vinegar; 2 tsp sugar; 1/4 tsp salt; 1 tbsp cornstarch + 2 tbsp water (mixed in small bowl. ); 1/3 cup soy sauce (or tamari for gluten-free); 3 tbsp maple syrup; 1 tsp rice vinegar; 2 tbsp water; 1 clove garlic (minced); 1/2 tsp ginger (minced); 1 tbsp olive oil; 2 portobello mushrooms (medium, stems removed, sliced 1 inch thickness); 2 seaweed wraps (nori); 1 avocado (sliced ); 1/2 cucumber (peeled and sliced into thin 1/4 inch strips); 1 small red pepper ((or 1/2 large) sliced into thin 1/4 inch strips); sesame seeds (optional)