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