Kumara rösti with portobello mushrooms

Name: Kumara rösti with portobello mushrooms
Ingredients: 1 large kumara (orange sweet potato) (500g); 1/2 cup (35g) panko (japanese) breadcrumbs; 1 cup (80g) grated parmesan; 2 eggs; 2 clove garlic, crushed; 1/4 cup (60ml) olive oil; 80 gram (2½ ounces) butter, chopped; 1/3 cup lightly packed fresh flat-leaf parsley leaves, chopped finely; 2 teaspoon fresh thyme leaves, chopped finely; 2 tablespoon finely chopped fresh chives; 6 portobello mushrooms (480g); 150 gram (4½ ounces) baby spinach leaves; 1/4 cup (20g) shaved parmesan; 1 lemon (140g), cut into wedges