In a small bowl, whisk together egg, almond flour, protein powder, heavy cream, baking powder, cinnamon, and salt.
Microwave the mixture in a mug for 60–75 seconds until set, then cut into cubes.
In another bowl, whisk egg, heavy cream, sweetener, cinnamon, ginger, nutmeg, allspice, and vanilla to make the custard.
Toss the bread cubes in the custard until fully coated.
Heat butter in a skillet over medium heat.
Add coated cubes and cook 2–3 minutes per side until golden and crisp.
Add optional toppings and serve warm.