Prepare and measure everything before starting (mise en place). Separate the 4 eggs while they are cold — yolks in one medium bowl, whites in a perfectly clean, dry mixing bowl. Cold eggs separate more cleanly; dry bowls prevent fat contamination that would prevent whites from whipping.

Warm the milk slightly: place the milk in a microwave-safe jug or small saucepan and warm until just tepid (about 100–110°F / 38–43°C). Warm milk integrates more easily with the melted butter and vanilla, producing a silkier batter and helping the sugar dissolve; don’t make it hot or it will cook the yolks when combined.

In a large mixing bowl, whisk together the flour, granulated sugar, light brown sugar, baking powder and salt. Sifting is optional but recommended if your flour is clumpy. Dry ingredients evenly distributed give an even rise and avoid streaks of baking powder in the finished pancake.

Split the vanilla bean lengthwise and scrape the seeds with the back of a knife into the warmed milk. Add the honey and the melted, cooled butter to the milk and whisk until the honey dissolves. The pod seeds release intense fragrance; warming the milk helps bloom the vanilla aromatics so the batter smells of real vanilla rather than extract.

Whisk the egg yolks lightly and stir them into the milk mixture so the yolks temper and incorporate without scrambling. If the milk is warm, this prevents curdling and ensures a smooth, unified wet mix.

Make a well in the center of the dry ingredients and pour in the wet ingredients. Fold gently with a spatula just until the flour streaks disappear. It’s okay if the batter is slightly lumpy — overmixing develops gluten and yields tough pancakes. The goal is just combined, smooth enough to hold air when whites are folded in.

With an electric mixer (or a very vigorous whisk), beat the egg whites until foamy. If using, add 1/8 tsp cream of tartar at this point to stabilize the foam. Continue beating to soft peaks, then toward firm glossy peaks — you want peaks that hold shape but are still slightly glossy so they fold easily (overbeaten whites become dry and won’t incorporate well).

Temper the whipped whites: scoop about one-quarter of the whipped whites into the batter and fold briskly to lighten the base (this makes the batter easier to fold the rest of the whites into). Then gently fold in the remaining whites in 2 additions using a broad spatula: lift from the bottom and fold over, rotating the bowl. Folding preserves the air you created in the whites — that air is what makes these pancakes pillowy.

Heat a nonstick skillet or griddle over medium-low heat. Brush with the 1 tablespoon butter and wipe off excess with a paper towel (a thin film gives a golden sear without smoking). Cooking at medium-low gives the interior time to set while the outside caramelizes; too-hot pans burn the surface before the center cooks.

Spoon or ladle batter (about 1/4 cup per pancake for 3–4" pancakes) onto the hot skillet. Cook gently until small bubbles form and the edges look set, about 2–3 minutes. Flip with a thin spatula and cook the second side until deep golden, about 1–2 minutes more. Resist pressing down — that releases the air and flattens the pancakes.

Keep finished pancakes warm in a single layer on a wire rack in a low oven (200°F / 95°C) while you cook the rest; stacking traps steam and makes them soggy. Serve immediately with a drizzle of honey and, if desired, a pat of butter and a sprinkle of extra brown sugar or a few flaky sea salt crystals to highlight the caramel notes.

Optional finishing: for a caramelized honey glaze, warm 2 tablespoons honey in a small pan with 1 teaspoon unsalted butter and a pinch of salt until glossy; brush onto pancakes right before serving for extra sheen and a deep, honeyed finish.