Well, this is a little after Chaucer's time, but this is what the OED says:
Of food, liquid, etc.: so hot as to make a whistling or hissing sound. More generally: very hot. Occas. of a person, the weather, etc.
c1390 [see sense 1]. a1586 (a1500) Freiris Berwik (Maitland) l. 356 Thair is ane pair of capounis pypand het [1568 Bannatyne het pypand]. 1601 P. HOLLAND tr. Pliny Hist. World II. 141 Beanes..fried all whole as they be, and so cast piping hot into sharp vineger. 1657 R. LIGON True Hist. Barbados 10 When we had climed..Being painfully and pipeing hot. 1707 J. STEVENS tr. F. de Quevedo Comical Wks. (1709) 234 A Mutton-Pye,..piping hot out of the Oven. 1761 L. STERNE Life Tristram Shandy IV. xxvii. 176 The chesnut, some how or other, did fall perpendicularly and piping hot into it. ?1809 S. T. COLERIDGE Madman & Lethargist in Poems 1787-1833 415 He fell, Like devil piping hot from hell. 1826 Let. 11 July in G. Jones Sketches Naval Life (1829) 180 Coffee is brought piping hot, and so they drink it. 1844 DICKENS Martin Chuzzlewit xlv. 517 Attended by another being with an oblong box upon his head, from which a banquet, piping hot, was taken out and set upon the table. 1888 J. W. BURGON Lives Twelve Good Men II. xi. 316 The day having been piping hot. 1904 J. LONDON Sea-wolf xxxix. 362 At seven a substantial and piping hot breakfast put new life into me. 1945 H. GERBER Fish Fare 56 Smoor in pan till the fish is brown and tender; serve piping hot. 1985 L. BLUE Kitchen Blues 124 Sprinkle the bananas with castor sugar..and lemon juice, and eat them piping hot.
Sense 1 that they referred to was the Chaucer quote above with this definition: "Shrill, high-pitched; whistling; having a shrill, high-pitched, or weak voice; (Eng. regional (south.)) wheezing. Recorded earliest in piping hot adj. at Special uses 1."