Prepare the batter. Pour milk into a blender, add eggs, add white wheat flour, salt, sugar, and vanilla extract. Blend well until a smooth, consistent mixture forms. You can also use a regular mixer, but remember, the smoother the batter (which is easier to achieve with a blender), the better.
Preheat the oven to 425 degrees F (220 degrees Celsius). Place the baking dish in the oven immediately so it heats up with the oven. Then, when the oven reaches the temperature specified in the recipe, carefully, using oven mitts, place the sliced pieces of butter at the bottom of the dish. The butter should melt fairly quickly - about 1 to 1.5 minutes. Once it's melted, carefully, using oven mitts, remove the dish. Tilt the dish forward and backward to coat approximately 2 inches (5 cm) of the dish's sides with the melted butter. Place the dish back on the kitchen counter or table. Don't turn off the oven, as you'll need to put the dish back in shortly.
Now, slowly and carefully pour the previously prepared batter into the center of the dish. Before pouring, it’s a good idea to blend the batter once more to aerate it further. Be cautious! It’s very important. The initial impulse might be to mix the butter with the batter, but don’t do it! The butter should remain on the edges.
Immediately after pouring the batter, place the baking dish into the oven (which is already preheated to 220°C/425°F) and bake for about 15-17 minutes. Important! Do not open the oven door during baking, as the pancake may deflate. Serve the baked pancake with your favorite toppings. Remember, it’s normal for the pancake’s edges to be the puffiest right after taking it out of the oven. They might deflate slightly after a few minutes.