Step 1: In a large, shallow dish (like a pie plate or baking dish), whisk together the eggs, whole milk, heavy cream, granulated sugar, vanilla extract, ground cinnamon, ground nutmeg, and a pinch of salt until thoroughly combined and slightly frothy. Ensure no streaks of egg white remain.
Step 2: Place the bread slices into the egg mixture, one or two at a time, ensuring they are fully submerged. Let them soak for 30 seconds to 1 minute per side for standard slices, or up to 2-3 minutes per side for very thick slices. The bread should absorb a good amount of liquid without becoming overly saturated or falling apart.
Step 3: While the bread soaks, heat a large non-stick skillet or griddle over medium heat. Add 1 tablespoon of unsalted butter and swirl to melt and coat the pan. The butter should be shimmering.
Step 4: Carefully lift each soaked bread slice, allowing any excess batter to drip off. Place the slices onto the hot skillet, making sure not to overcrowd the pan (cook in batches if necessary). Cook for 3-4 minutes per side, or until deeply golden brown and cooked through. The internal temperature should be around 165°F (74°C).
Step 5: Transfer the cooked French toast slices to a wire rack set over a baking sheet and place them in a warm oven (around 200°F / 93°C) to keep them warm while you cook the remaining slices. Add more butter to the pan as needed for subsequent batches.
Step 6: Serve the French toast immediately with your favorite toppings such as warm maple syrup, a dusting of powdered sugar, fresh berries, or whipped cream. Enjoy your homemade, perfectly custardy French toast!