Sandwich Saus Prancis Vegetarian

Bahan-bahan (4 porsi)

• 1 yellow onion ($0.32)
• 3 portobello mushroom caps (about ½ lb.) ($3.99)
• 2 Tbsp butter ($0.20)
• 1/8 tsp salt ($0.01)
• 1/8 tsp freshly cracked black pepper ($0.01)
• 1/4 tsp dried thyme ($0.02)
• 1/4 tsp dried oregano ($0.02)
• 2 cups vegetable broth* ($0.26)
• 1 Tbsp kecap ($0,06)
• 1/2 Tbsp brown sugar ($0.02)
• 1/8 tsp garlic powder ($0.01)
• 4 6 -inch French or Hoagie rolls ($1.66)
• 4 slices provolone ($1.00)