01 - Rinse and hull the strawberries, then cut them in half. Arrange them evenly in a rectangular mold or loaf pan (approximately 8 x 4 inches).
02 - In a small saucepan, combine the milk, sugar, and agar-agar. Whisk thoroughly until the agar-agar is completely dissolved.
03 - Place the saucepan over medium heat. Bring the mixture to a gentle simmer while stirring constantly. Continue simmering for 2 minutes to fully activate the gelling properties of the agar-agar.
04 - Remove from heat and stir in the vanilla extract until evenly incorporated.
05 - Allow the milk mixture to cool for 2–3 minutes, then gently pour it over the arranged strawberries in the mold. Tap the mold lightly on the counter to release any trapped air bubbles and ensure even distribution of the fruit.
06 - Let the yokan cool to room temperature, then refrigerate for at least 3 hours, or until completely firm and set.
07 - Once fully set, unmold onto a cutting board and slice into rectangular portions. Garnish with fresh mint leaves if desired.