This recipe is easy to scale based on how many servings you wish to make. I make two slices of bread for each serving. I have made a single serving for myself using a single egg and you could easily scale it up to a dozen eggs to serve a crowd gathered at your table. I am usually making this recipe for four people, so this recipe is written for four servings or eight slices of bread. This recipe is easy to adapt to your preferences. Instead of granulated sugar, you can use brown sugar or honey if you prefer. I like to combine equal parts of whole milk and heavy cream, but you can adjust the ratio or use what you have on hand. I cook one serving at a time in a skillet or more if I have set up my cast iron griddle. If you need to hold some of the servings to keep them warm while you finish your batch, the cooked slices can be placed on a wire cooling rack set on a sheet pan in an oven held at 200 - 225 degrees.
Place a griddle pan or skillet over low heat while you prepare the custard.
Combine the eggs, sugar, heavy cream, milk, salt, and vanilla in a wide bowl. I like to use my Pyrex casserole dish because it is wide enough for two slices of bread at a time. Whisk until smooth.
Add a small pat of butter to the warm skillet or griddle. Allow the butter to melt and begin to bubble.
Add two slices of bread to the bowl with the custard. Turn the bread gently to expose both sides to the custard. Do not soak the bread in the custard. You want the bread to absorb a bit of the custard without becoming soggy and falling apart. A few seconds on each side will be enough time.
Carefully lift a slice of bread from the custard, allowing any excess to drip back into the bowl and transfer to the warm skillet. Repeat with the other slice of bread. Increase the heat to medium-low and cook for 3 to 5 minutes before gently lifting the edge of each slice to check for browning. You want the slices to develop a golden-brown hue without burning. The amount of time required will vary based on how large your cooking surface is and how many slices you are cooking at a time. Be patient. Cooking the slices slowly will create a caramelized exterior and soft interior. The few extra minutes will be worth it.
When the slices are golden brown and beginning to firm up just a bit in the center, gently flip each slice. Add a little more butter if needed.
Continue cooking the slices over low heat, adjusting as needed to brown gently. If you like the center fully cooked, you can test each slice by gently pressing the center of the bread with your finger. If the custard is fully cooked, the slice should spring back gently after pressing it. When both sides are golden brown and the center has set to your liking, the toast can be transferred to a warm oven for holding or to a plate for serving immediately.
Serve topped with maple syrup, sifted powdered sugar, or whipped cream with fresh berries.