Place goat cheese, scallions, mint, red-pepper flakes, and reserved piquillo liquid in a bowl. Zest and then juice lemons into the bowl, straining seeds. Mix until well combined.
Using a small spoon, fill each pepper with about 2 tablespoons of the goat cheese mixture. Alternatively, pipe the mixture into the peppers. Place on a serving plate, and sprinkle with red-pepper flakes; garnish with spring onions if desired. Serve immediately, or cover and refrigerate until ready to serve, about 1 hour.
Piquillos are small, sweet fire-roasted red peppers that are packaged only in Spain. Jars of piquillos are available online and at specialty-food stores.
GOSH!! These were so delicious. I served these at a wine and cheese party I hosted. I expected the peppers to be a smaller than they were, and maybe they vary, but one stuffed pepper was quite filling. The amount of goat cheese can be expensive but it's worth it, they were tasty! My guests absolutely loved them. Keep in mind the peppers are delicate so piping is the best way to go.