This paper explores a small but intriguing group of medieval poems preserved in a manuscript known as chansonnier f, a handwritten songbook from the late Middle Ages. The focus is on a series of sonnets written in Old Occitan, a historical language once widely spoken in southern France. One of these poems is attributed to Blacasset, a 13th-century troubadour. However, whether Blacasset truly wrote it is far from certain — and that mystery lies at the heart of this study. The research asks several key questions: Are these sonnets authentic medieval works or later imitations? Who actually wrote them? And why would someone choose to attribute one of them to Blacasset in particular? For a long time, scholars suspected that Jehan de Nostredame, a 16th-century writer famous for inventing or embellishing troubadour biographies, and the younger brother of the more well-known Michel de Nostredame, aka Nostradamus, may have forged the poems. By closely examining their language and poetic structure, the study suggests that they were likely composed in the 15th century, much later than Blacasset’s lifetime. The poems show a blend of Occitan and French features, reflecting a period when these languages strongly influenced one another. This linguistic mix helps narrow down when and where the poems were written. The paper also places the sonnets within their broader historical and political setting. Subtle references in the poems may allude to tensions and alliances involving Provence and the ruling houses of Aragon and Anjou, offering clues about the political concerns of their time.