Step 1: Prepare the mango puree. Peel and pit the ripe mango. Cut the flesh into chunks and place them in a blender. Blend until completely smooth. If desired, strain through a fine-mesh sieve for an extra-smooth puree.
Step 2: Rim your glasses. On one small plate, pour a thin layer of fresh lime juice. On another small plate, spread a thin layer of coarse salt or sugar. Dip the rim of each serving glass first into the lime juice, then into the salt/sugar, twisting gently to coat.
Step 3: Combine ingredients. In a cocktail shaker, combine 1 cup of mango puree, the blanco tequila, fresh lime juice, orange liqueur, and agave nectar (if using).
Step 4: Shake well. Add a generous amount of ice to the shaker. Secure the lid and shake vigorously for 15-20 seconds until the mixture is thoroughly chilled and well-combined.
Step 5: Serve the mango margarita. Fill your prepared, rimmed glasses with fresh ice. Strain the contents of the cocktail shaker into the glasses.
Step 6: Garnish and enjoy. Garnish each mango margarita with a lime wedge or a slice of fresh mango. Serve immediately and savor your tropical creation!