01 - Rinse strawberries thoroughly, remove the green hulls, and slice each berry in half lengthwise. Distribute the halves evenly across the bottom of an 8 x 4-inch rectangular loaf pan or similar mold.
02 - In a small saucepan, add the whole milk, granulated sugar, and powdered agar-agar. Whisk vigorously until the agar-agar is completely dissolved and no lumps remain.
03 - Place the saucepan over medium heat and bring the mixture to a gentle simmer while stirring constantly. Maintain the simmer for 2 minutes to ensure the agar-agar is fully activated.
04 - Remove the saucepan from the heat source. Stir in the vanilla extract until fully incorporated into the warm milk mixture.
05 - Let the mixture cool for 2 to 3 minutes, then gently pour it over the arranged strawberries. Lightly tap the mold on the counter to release trapped air bubbles and settle the fruit evenly.
06 - Allow the yokan to reach room temperature, then refrigerate for a minimum of 3 hours or until completely firm and set.
07 - Unmold the set yokan onto a cutting board. Slice into portions and garnish with fresh mint leaves if desired.