Make the crust

1. Spray a 9-inch tart pan with non-stick baking spray and preheat oven to 325°F.
2. Add the vanilla wafer crumbs and sugar to a medium sized bowl and stir to combine. Add the melted butter and stir until well combined.
3. Pour the mixture into the tart pan and press the crumbs into the bottom and up the sides of the pan. Pack it firmly. Use a measuring cup or glass with sharp corners and straight edges to help and use your fingers for the sides of the pan.
4. Bake for 7 minutes, then remove from oven and set aside to cool completely. If you want to speed up cooling, you can put it in the fridge or the freezer.

Make the filling

1. In a small bowl, sprinkle gelatin over cold water. Stir to moisten all of the gelatin powder. Set aside for about 5 minutes.
2. Add cornstarch and sugar to a saucepan and whisk together to break up any lumps in the cornstarch. Add the champagne and heat over medium heat, gently stirring the whole time, until the champagne mixture just begins to boil. Remove from heat. Note: You don’t want to turn the heat up too high to speed this process up. You want it to have time to thicken properly. If your stove runs hot, turn the heat down to more of a medium-low heat.
3. Heat gelatin for about 10 seconds, until melted, then whisk gelatin into champagne mixture until smooth. Pour the mixture into another bowl and let cool until it’s about room temperature. You want it cool enough that it won’t melt the whipped cream, but not so cool that the gelatin is getting too firm and will clump.
4. In another bowl, whip heavy whipping cream and powdered sugar until it starts to thicken.
5. Add the mascarpone cheese and whip on low speed until it’s incorporated and no longer lumpy, then increase to medium speed. Whip just until the whipped cream thickens and holds shape.
6. Carefully fold cooled champagne mixture (it should be thickened and jiggly, but not firm yet) into mascarpone cheese mixture in two parts, until well combined.
7. Spread mixture evenly into crust and refrigerate until firm, 2-3 hours.

Add the toppings

1. Combine champagne, cornstarch and sugar for the glaze in a small bowl. Microwave in 10 second increments until it begins to boil and thicken, about 30-40 seconds. Set aside to cool a bit.
2. Layer sliced strawberries on top of the tart filling, then brush cooled glaze onto strawberries with a pastry brush.
3. Refrigerate tart until glaze it cool, about 30 minutes to an hour, then serve.