Kentang Tumbuk Bayam dan Feta

Bahan-bahan (6 porsi)

• 2 russet potatoes (about 2.5 lbs.) ($1.85)
• 3 Tbsp butter ($0.27)
• 1/4 tsp garlic powder ($0.02)
• 1/2 tsp salt ($0.03)
• Freshly cracked pepper ($0.05)
• 1/4 cup milk ($0.11)
• 2 cups (packed) fresh spinach ($1.34)
• 2 oz crumbled feta ($1.12)