Preheat the oven to 350°F and line a baking sheet (or two) with parchment paper.
In a small bowl, combine the strawberries, 1 tablespoon sugar, and 1 teaspoon vanilla. Stir to coat the berries and set aside to macerate.
Slice the brioche into 4 to 6 1-inch-thick slices.
In a food processor, chop the almonds until they are a fine meal.
Add the butter, remaining 2/3 cup sugar, flour, cornstarch, egg, almond extract, and remaining 1 teaspoon vanilla extract. Purée until smooth.
Spread an even layer of the almond cream (frangipane) onto each slice of bread. (If you have extra cream, cut more bread.) Top with strawberries and sliced almonds.
Bake for about 20 minutes, until the frangipane has puffed slightly and is golden brown. Let cool about 10 minutes to set the frangipane, then dust with powdered sugar and serve.
Notes
If using almond meal instead of slivered almonds, you'll need ¾ cup. Skip the chopping in step 4.
In Step 5, the almond cream can be made in a stand mixer using the paddle attachment, a hand mixer, or by hand. Beat the butter and sugar together, then add the almond, then egg and extracts, and finally the flour and cornstarch.