Preheat your oven to 350°F (175°C). In a mixing bowl, combine the all-purpose flour and granulated sugar. Add in the cold, cubed unsalted butter, mixing until crumbly. Press this mixture firmly into a tart pan, pricking the base with a fork. Bake for 20 minutes until golden brown and fragrant.

Whisk the cornstarch and sugar together in a saucepan over medium heat. Gradually stir in the brut champagne, cooking the mixture until it thickens, about 5-7 minutes.

Fold in the sliced strawberries gently, ensuring they are well-coated. Pour this delightful filling into the cooled tart crust, spreading it evenly. Bake for an additional 10-15 minutes until the filling is bubbly and golden.

Cool the tart at room temperature for about two hours before serving.

Optional: Drizzle with whipped cream before serving.