To a blender, add 3 cups ice, 1½ cups tequila, ½ cup agave syrup, 2 cups limeade, 1 cup fresh spinach, ½ cup chopped Asian pear, ½ cup fennel juice (recipe follows), or substitute 2 tbsp fennel fronds, and 1 cup chilled water. Blend until slushy and pour into glasses. Garnish each with a fennel frond.
Add ½ fennel bulb, trimmed and chopped (about 2 cups), 1 cup water and ½ tsp salt to a blender; purée. Strain through a fine mesh sieve and chill for up to a day.
Recipe adapted from: Hunt, Michelle P.E. and Laura Panter. "Mistletoe Margarita." Food & Drink. Holiday 2017.