FILLING: In a large bowl, combine the grapes, flour, sugar, vanilla and almond extracts, lemon juice and salt; toss to coat the grapes.
TOPPING: In a medium bowl, whisk together flour, almond flour, sugar, baking powder and salt. Work the butter into the flour mixture with your fingers until it looks like coarse meal with pea-size bits of butter. Lightly beat the egg and heavy cream in a small bowl; add to the flour mixture and stir until a sticky dough forms.
Spread the grape filling in an 8-inch square baking dish. Drop heaping tablespoonfuls of the biscuit topping over the grapes, leaving a small space between each spoonful. Sprinkle the topping with sugar and the almonds.
Bake until the biscuits are golden brown and puffy and the filling is bubbling, about 40 to 50 minutes. Transfer to a rack and let cool at least 30 minutes before serving.