Bring water to a boil and add eggs. Cook at hard boil for 9½ minutes. Transfer to ice bath to cool, then peel and rinse.

Slice eggs crosswise (perpendicular to length) to create oval halves that stand upright. Remove yolks to a bowl and refrigerate. Trim bottom tips of whites so they stand straight.

Heat butter in frying pan over medium heat. Add garlic as butter melts, then stir in spinach. Cook 5 minutes until wilted and moisture evaporated. Cool completely.

In blender, combine spinach mixture, egg yolks, mayo, mustard, lemon juice, paprika, hot sauce, and potato flakes. Blend until smooth.

Refrigerate filling until completely cool. If not thick enough to stand tall, add more potato flakes. Transfer to piping bag with star tip.

Place egg whites on platter. Pipe filling into whites, bobbing tip up and down while moving vertically to form tree shape.

Use toothpicks to add 5-6 pieces of red pepper to each tree as decorations. Top with yellow pepper stars.

Grate Parmesan cheese over trees with microplane grater to create 'snow' effect. Serve immediately.