Butter a 9x13-inch baking dish and spread the bread cubes evenly in the pan. Let them sit uncovered for 1-2 hours to dry out slightly if your bread is very fresh.
In a large bowl, whisk together the eggs and sugar vigorously for 30 seconds until the mixture becomes pale and slightly thickened. Add the milk, cream, honey, vanilla, cinnamon, nutmeg, and salt, whisking until completely smooth.
Pour half of the custard mixture over the bread cubes, pressing down gently with a spatula to submerge. Wait 5 minutes, then pour the remaining custard over top. Let the bread soak for 20-30 minutes at room temperature, pressing down occasionally.
While the bread soaks, prepare the honey cinnamon butter by beating together the softened butter, 3 tablespoons honey, and 1 teaspoon cinnamon until light and fluffy, about 2 minutes.
Preheat your oven to 350°F (175°C). Drop spoonfuls of the honey cinnamon butter across the top of the soaked bread pudding, leaving some areas uncovered for contrast.
Cover the dish tightly with aluminum foil and bake for 30 minutes. Remove the foil and continue baking for 25-30 minutes until the top is golden brown and the center is set but still slightly jiggly.
Remove from the oven and let rest for 10 minutes before serving. The pudding will firm up as it cools slightly. Serve warm with extra honey cinnamon butter drizzled on top if desired.