01 - Rinse strawberries thoroughly, remove the green hulls, and slice each berry in half lengthwise. Arrange the halved strawberries evenly in an 8 x 4-inch rectangular loaf pan, placing cut sides down for an attractive presentation.
02 - In a small saucepan, add whole milk, granulated sugar, and powdered agar-agar. Whisk vigorously until the agar-agar powder is completely dissolved and no lumps remain.
03 - Place the saucepan over medium heat and bring the mixture to a gentle simmer while stirring continuously. Once simmering, maintain the heat for 2 minutes to fully activate the gelling properties of the agar-agar.
04 - Remove the saucepan from heat and immediately stir in the vanilla extract until fully incorporated into the warm milk mixture.
05 - Let the milk mixture cool for 2-3 minutes until slightly thickened. Gently pour over the arranged strawberries in the mold. Lightly tap the pan on the counter to release trapped air bubbles and distribute the fruit evenly.
06 - Allow the yokan to cool completely at room temperature for 30 minutes, then refrigerate for at least 3 hours or until the dessert is fully set and firm to the touch.
07 - Once fully set, run a thin knife around the edges of the pan and invert onto a cutting board. Slice into rectangular portions and garnish with fresh mint leaves if desired.