Place the first four ingredients into a microwave safe mug.
Microwave for 90 seconds, remove bread from mug and cut into cubes.
Repeat step 1-2, making two mug breads and cutting them into cubes.
In a small bowl combine ingredients for the syrup mixture.
Pour into a small casserole dish and top with cubed bread.
Combine ingredients for the filling in a bowl and whisk together.
Pour this mixture overtop of the bread, cover and refrigerate overnight (8 hours).
Bake the next day at 350 for 40-45 mins.
Top with butter and sugar-free syrup.