Step 1Put the butter in a medium bowl and beat it with a wooden spoon until it turns soft and creamy. Stir in the lime zest, lime juice, salt, white pepper, chopped cilantro, garlic and chile flakes.
Step 2Spoon onto a sheet of plastic wrap and roll into a sausage shape. Twist the ends of the wrap to seal the flavored butter. Chill until firm.
Step 3This makes a generous one-half cup butter, more than is needed for the remainder of the recipe; the butter will keep, covered and refrigerated, for up to 3 days.
Step 1Wilt the spinach in a pan with a splash of water. Drain in a sieve and, when cool, squeeze hard with your hands to remove as much moisture as possible. Roughly chop and put aside.
Step 2Combine the flour, baking powder, whole egg, melted butter, salt, cumin and milk in a large mixing bowl and whisk until smooth. Add the green onions, chile and spinach, and mix with a fork. Beat the egg white to soft peaks and gently fold it into the batter.
Step 3Pour a small amount of olive oil into a heavy frying pan and place on medium-high heat. For each pancake, ladle 2 tablespoons of batter into the pan and press down gently. You should get smallish pancakes, about 3 inches in diameter and three-eighths-inch thick. Cook until you get a good golden-green color, about 2 minutes to a side. Transfer to paper towels and keep warm. Continue making pancakes, adding oil to the pan as needed, until the batter is used up.
Step 4To serve, pile up 3 warm pancakes per person and place a pat of flavored butter on top to melt.