Special equipment: Plancha or pancake griddle pan, 1 newspaper (preferably Spanish!), 6-inch bamboo skewers
Place the lamb pieces on the bamboo skewers (3 to 4 pieces per skewer) and place in a large baking pan. Coat lamb skewers with marinade and cover. Refrigerate marinated skewers overnight.
Heat a plancha or griddle pan over high heat. Season the skewers with kosher salt. Sear each lamb skewers, about 1 minute per side. Serve on a large platter over the Piperrada.
Combine shallot, guindilla pepper, thyme, chives, rosemary, cumin, fennel seed, mustard seed, saffron, and paprika together in a medium bowl. Add the lemon juice and slowly add olive oil while whisking thoroughly.
Heat a plancha or pancake griddle pan over medium-high heat and carefully blacken the red peppers on all sides. Once sufficiently charred, remove, wrap in the newspaper and set aside to cool. When the peppers are cool enough to handle, carefully pull out the seeds and peel away the charred skin. Slice the peeled red pepper into thin strips and add to a medium bowl with garlic and whole thyme sprigs. Add olive oil, toss together, and marinate for at least 20 minutes, or up to 1 day ahead.