Bring the milk, heavy cream, butter and about 1 tsp of orange zest to a boil in a small saucepan.
250 ml Milk, 15 g Butter, 15 g Heavy Cream, 1/2 Blood or Regular Orange
Meanwhile, thoroughly mix the egg, flour and sugar in a medium-sized heat-proof bowl.
1 Egg, 65 g Flour (Bread), 50 g Sugar
Add the boiled milk little by little to the egg mixture, whisking constantly.Start slow and whisk constantly. You want to temper the mixture, not scramble the eggs. Add the vanilla and juice from the half of the orange. Strain into another bowl or pitcher and cover.Straining it will remove the zest and and any small pieces of cooked egg. 1 tsp Vanilla Extract or Paste
Put the covered batter in the fridge overnight (at least 12 hours).The batter can rest anywhere between 12-48 hours. Preheat your oven to 475 Fahrenheit or 250 Celsius. Liberally butter the Canelés molds with softened butter. Using a pastry brush to butter the molds. Note: Check the max temperature allowance for your mold/pan. Some may only go up to 450F, so just pre-heat to the maximum allowed (if not 475F). Take the batter out of the fridge and whisk a couple of times in case of settling. Pour into the molds to about 3/4 full.
Bake for 10 minutes, then lower the temperature to 350F / 175C and bake for another 55-60 minutes.
Remove the Canelés from the mold immediately and cool. You can flip them out onto a wire rack or counter. You may need to tap the molds to release them. If the bottoms are still light, put them back in the mold and bake again for a few more minutes.