In a small bowl, combine strawberries, maple syrup, coffee granules and cinnamon. Set aside.
Trim the crust from both ends and all four sides of the brioche loaf to form a rectangular log. Slice in half lengthwise and cut each half into 10 equal cubes.
With a paring knife, score a square 3/4 of the way down each cube 1/8 inch in from edges. Arrange cubes, score side up, on a parchment lined baking sheet. Toast in an °oven for 3 minutes until golden brown. Remove from oven. While still hot, press down on the small square of each cube to create the cavity for the filling. Let cool.
Spoon or pipe 1 tsp mascarpone into each cube.
Top each with 1/2 tablespoon strawberry mix.
Garnish with mint just before serving.
Make-Ahead: Toasted brioche cube shells can be kept frozen in an airtight container for up to 3 days. Let thaw before filling.