Step 1: Prepare the Pink Lemonade Base. In a blender, combine the fresh or frozen strawberries, fresh lemon juice, granulated sugar, and 1 cup of cold water. Blend until completely smooth. Taste and adjust sugar if needed for your desired sweetness. If using fresh strawberries, you might want to strain the mixture through a fine-mesh sieve to remove seeds for a smoother drink, then discard solids.
Step 2: Dilute the Lemonade. Pour the strawberry-lemon mixture into a large pitcher. Add the remaining 2 cups of cold water and stir well to combine. Chill in the refrigerator until ready to serve.
Step 3: Make the Whipped Cream. In a large, chilled mixing bowl (metal or glass bowls work best when chilled), combine the very cold heavy cream, powdered sugar, and vanilla extract. Beat with an electric mixer on medium-high speed until stiff peaks form. Be careful not to overbeat, as it can turn grainy.
Step 4: Assemble the Whipped Pink Lemonade. Fill individual glasses with ice. Pour the chilled pink lemonade base into each glass, filling about three-quarters of the way. Top generously with the freshly made whipped cream.
Step 5: Garnish and Serve. Garnish each glass with a fresh lemon slice, a whole strawberry, or a few strawberry slices, if desired. Serve immediately and enjoy your creamy, refreshing Whipped Pink Lemonade!