4 metal or wooden skewers, soaked in water 30 minutes if wooden
Heat a grill to medium-high heat or place a grill pan on the stove over medium-high heat. Generously grease the grill grates with the vegetable oil. Slide 5 strawberries on a skewer, pushing the skewer through the cores. Repeat this process to assemble 3 more skewers. Place the skewers on the grill and cook, turning as needed, until dark grill marks are created, 3 to 4 minutes per side. Remove half the strawberries from the skewers to a large bowl and use a fork to mash them. Stir in the remaining strawberries and set aside.
Grill the cake slices until they have grill marks, 30 to 45 seconds per side (do not let the cake slices cook for more than 1 minute or they will start to stick).
Combine the whipping cream, mascarpone and confectioners' sugar in the bowl of an electric mixer. Whip until stiff peaks form, about 4 minutes. Plate the cakes individually and top each with some strawberries. Drizzle the balsamic glaze over the berries. Dollop the whipped cream on top and garnish each plate with a sprig of fresh mint. Serve immediately.