Step 1: Prepare the Whipped Cream. In a very cold bowl (preferably metal, chilled for 10-15 minutes) and with cold beaters, combine the heavy whipping cream, powdered sugar, and vanilla extract (if using). Whip on medium-high speed until stiff peaks form. Be careful not to over-whip.
Step 2: Prepare the Bread. Lay the bread slices flat. Using a sharp serrated knife, carefully trim the crusts from all four sides of each bread slice.
Step 3: Assemble the First Layer of Cream. Place one slice of trimmed bread on a clean surface. Spread a generous, even layer of whipped cream over the entire surface of the bread, ensuring it reaches the edges.
Step 4: Arrange the Strawberries. Carefully arrange 5-6 strawberries on the cream, pressing them gently. Arrange them in a pattern that will look visually appealing when the sandwich is cut diagonally (e.g., one in each corner, one in the center, or in a diagonal line).
Step 5: Apply the Top Layer of Cream. Fill any gaps between the strawberries with more whipped cream, then spread another even layer of cream over the top of the strawberries, ensuring they are completely covered and the surface is smooth.
Step 6: Place the Top Bread Slice. Gently place the second slice of trimmed bread directly on top of the cream-covered strawberries. Press down very lightly to ensure it adheres.
Step 7: Wrap and Chill. Tightly wrap the assembled sandwich in plastic wrap. This is crucial for the sandwich to set and for clean cuts. Repeat for the second sandwich. Place the wrapped sandwiches in the refrigerator for at least 30 minutes, or preferably 1-2 hours.
Step 8: Cut and Serve. Once chilled, unwrap the sandwich. Using a very sharp, long serrated knife, cut the sandwich diagonally from corner to corner. Wipe the knife clean between each cut for the cleanest edges. Serve immediately and enjoy your beautiful Japanese Strawberry Sando!