Step 1 In a small saucepan, heat the milk over high heat just until it comes to a good simmer (do not let it boil), then remove from heat and cool the milk to lukewarm.
Step 2 While the milk is cooling, sprinkle the yeast over the warm water, then stir to combine. Set it aside until it dissolves and begins to bubble, about 5 minutes.
Step 3In a medium bowl, sift together the flours and 1/2 teaspoon salt, and make a well in the center. Add the yeast mixture and 1 cup of the warm milk. Slowly incorporate the flour into the liquid with a spoon or your hands, gradually mixing it in to form a smooth batter. Beat the batter for 1 minute to fully incorporate the ingredients. Cover the bowl loosely with plastic wrap and set it aside to rise until the batter is full of bubbles and light in texture, 2 to 3 hours.
Step 4Roast the pepper over high heat on top of a stove burner, turning with tongs until the skin is completely charred. Alternatively, toast under a broiler on all sides to char. Place the pepper in a plastic bag, and loosely cover to allow steam to loosen the skin. When cooled, peel and halve the pepper, discarding the core and seeds. Slice the pepper crosswise into one-eighth-inch strips. Set aside.
Step 5When the batter is light and bubbly, stir in the yolks and one-half cup of the milk. The batter will be elastic but should pour easily (if not, add more of the milk as needed). In a separate bowl, whisk the whites until they hold a soft peak; gently fold into the batter.
Step 6Heat a large frying pan over medium heat. Add 2 to 3 tablespoons butter and heat until the butter is melted and has stopped foaming. Ladle the batter into the pan to form 3-inch blini (about 2 tablespoons of batter per pancake) and cook until the tops are bubbly and the undersides browned, 1 to 2 minutes. Flip the blini over and cook the other side, about 1 minute. Place the blini on a plate, stacking them to keep them moist. Repeat until all the blini are cooked, using more butter as needed. This recipe makes 3 to 3 1/2 dozen blini. (Recipe can be prepared up to this point a day ahead. Place the cooked blini in an airtight container and refrigerate.)
Step 7Before serving, warm the blini in the microwave or in a 350-degree oven, wrapped in foil, for 15 to 20 minutes. Spread each pancake with a spoonful of tapenade and top each with 2 crossed strips of pepper. Plate 3 per serving.