My preferred method for hard boiled eggs:

• Place eggs in a 3 quart pot filled with cold water. Bring the water to a boil, cover, remove from heat and let sit for 10 minutes. Run eggs under cold water until fully chilled. Refrigerate 2+ hours before peeling.
• Peel boiled eggs. Slice in half, lengthwise. Transfer yolks to food processor or jar. Discard two egg whites leaving 12 deviled eggs total.
• Add spinach, mayo and mustard to yolks. Process or use handheld blender (my preferred method) until mixture is smooth. Start with 3 TB mayo then add more if needed. Salt and pepper to taste.
• Transfer yolk mixture to ziplock bag. Cut the bottom corner off of bag and pipe filling into egg whites.
• Top each egg with 4-5 diced pimentos.
• Refrigerate until ready to serve.