Pre-heat oven to 200 degrees F (~94 C).
Mix frozen blueberries with maple syrup and heat in the microwave for 3-4 minutes until heated through. They will release liquid but keep their shape.
Take 1/3 cup of the blueberry sauce and puree in a food processor. Set the rest of the sauce aside for later.
Beat eggs, half and half, vanilla and the blueberry puree in a long, shallow glass container.
Take one English muffin, split in half, and soak both halves in the purple mixture. Repeat until you fill the container. You may need to soak the muffins in batches. I did it in two batches. Leave them in the mixture for 4 minutes per side.
Melt one tablespoon butter and one teaspoon vegetable oil on a griddle over medium-high heat.
Add the English muffins and cook until cooked through and golden brown. Depending on your stove, this will take approximately 6 minutes per side. Repeat until you finish with all. Keep the French toast warm in the oven until ready to serve.
Take one-half of an English muffin and layer it with whipped cream and blueberry sauce. Cover with the second half and top with more whipped cream and blueberries.
Or, serve as dessert with vanilla ice cream and blueberry sauce. This is absolutely delicious.