In a large bowl, whisk together 5 large eggs, 6 cups milk, and 1 tsp. pure vanilla extract. Mix in 5 Tbsp. sugar and ½ tsp. salt, then gradually whisk in 3 cups flour.
Let rest at room temperature for 30 minutes.
Get out a large nonstick skillet, some unsalted butter, a ladle, and a spatula. Over medium heat, add a knob of butter to the skillet and let it foam.
Add a half-ladle of the thin batter in an even circular motion, swirling it into a large flat circle. Let it brown on one side for a minute or two, then flip with a spatula, and let it brown for 30 seconds or so on the other side.
Remove from pan and set aside on a large plate. Keep going, adding more butter as needed, and more batter, flipping away, until your batter is gone and you have enough delicious Finnish pancakes to serve 4–6 people.
Serve with maple syrup and fresh berries and even a dusting of confectioners’ sugar if you’re feeling fancy.