Crack eggs into a wide shallow bowl. Add whole milk, heavy cream, sugar, vanilla extract, cinnamon, nutmeg, and salt. Whisk vigorously for 30 seconds until completely smooth with no visible egg white streaks.
If using fresh bread, leave slices on a wire rack for 30 minutes to dry the surface slightly. Lay bread slices next to the stove, ready to transfer from custard to pan quickly.
Heat a large skillet over medium heat for 90 seconds. Add 1/2 tablespoon of butter and let it melt and foam without browning. Swirl to coat the base evenly.
Lay one or two bread slices in the custard and soak for 30 to 45 seconds per side. Lift and let excess custard drip back for 3 to 4 seconds before placing in the pan.
Cook the first side undisturbed for 2 to 3 minutes until deep golden-amber when the edge is lifted with a spatula. The slice should release cleanly; if it sticks, give it another 30 seconds.
Flip in one decisive motion. Cook the second side for 1.5 to 2 minutes until golden. Press the center gently with the spatula; it should feel set and springy throughout.
Transfer to a warm plate and repeat with remaining slices, adding fresh butter before each batch. Serve immediately with powdered sugar, maple syrup, and fresh fruit.
