In the bowl of a stand mixer with the whisk attachment, add heavy cream and confectioners' sugar and beat on high speed until soft peaks form. Fold in the mascarpone and beat until well combined. Transfer the whipped mascarpone cream to a serving bowl and refrigerate it while you're preparing the French toast.
Use a good bread knife to cut the brioche loaf into eight 3/4 inch slices. Reserve the rest for other uses.
In a shallow bowl enough to fit the brioche slice, whisk the eggs, milk, vanilla, sugar, salt, and cinnamon until well combined. Set aside.
Place a small knob of butter in a large, heavy nonstick skillet over low heat and let it melt slowly.
When butter is just melted and bubbling, raise heat to medium and bring to a sizzle. Place 2 slices of bread in the bowl with the egg mixture for about 5 seconds and quickly turn them to other side for another 5 seconds. Do not soak them.
Lift the slices out of the egg mixture with a spatula, gently shake off any excess, and place them on the pan. Cook 2 slices at a time and let them cook at a sizzle for about 2-2 1/2 minutes, until just golden brown on the bottom then flip them to the other side.
Test for doneness by pressing the center. The slices are coooked if the dent slowly springs back. If it remains, the interior is not yet cooked. Continue cooking at low heat, flipping occasionally, until done.
Repeat until you're done with all the slices.
Place them on 4 plates and serve immediately. Top with strawberries, mascarpone cream, maple syrup, powdered sugar, or whatever you like.