Portobello Gruyere Sandwich!

Ingrédients
4 Medium sized portobello mushrooms (de-stemmed and de-gilled)
1 Tbls butter
2 Cloves garlic
1 Pinch dried chili flakes
2 Tbls Olive Oil
6 to 8 Slices Gruyere or Swiss cheese
1 Cup Arugula
1/4 Onion, in thin slices
1/4 Water
Course Salt and Ground Pepper
Whole wheat hamburger buns or dinner rolls
Préparation
Mash Garlic and a pinch of salt/pepper into a bowl or mortar
Ad 1 Tbls olive oil and bring to a pasty consistancy
Rub a thin layer of paste onto mushroom caps (both sides)
In a skillet, on high heat
Bring remaining olive oil and butter to a hot sizzle
Stir in chili flakes
Add mushroom caps and cook until lightly brown
Add water, cover and cook until mushrooms are tender (2-3 min)
Place 2 slices of cheese on half of each roll
Toast both halves in oven @ 400
Combine arugula with onion slices
Place mushroom on cheese side of roll and top with arugula/onion mixture