The spelling of the word "plumpie" can be explained using the International Phonetic Alphabet (IPA). The initial sound is a plosive "p" sound followed by the "l" consonant. The "u" is pronounced as a short vowel sound and is followed by the "m" consonant. The second syllable starts with the "p" consonant and has a long "i" sound followed by the "e" vowel. Therefore, the correct spelling of this word is "plumpie" /plʌm.pi/.