Tumpukan Gratin Kentang Keju (Kaleng Muffin)

Bahan-bahan (12 porsi)

• Oil spray
• 1.2 kg / 2.4 lb starchy potatoes (, large long ones (Note 1))
• 30 g /2 tbsp butter (, unsalted)
• 2 g arlic cloves (, finely minced)
• 1/2 cup heavy / thickened cream
• 1 tsp fresh thyme leaves ((or 3/4 tsp dried))
• 1/2 tsp salt
• Black pepper
• 75 g / 2.5 oz gruyere cheese (sliced into 12 squares to fit into muffin tin (or other melting cheese, Note 2))
• 3/4 cup gruyere cheese ((or other melting cheese), shredded)