Bhashya
यथा अयं दृष्टान्तः, एवमेव खलु सोम्य अन्नस्य ओदनादेःअश्यमानस्य भुज्यमानस्य औदर्येणाग्निना वायुसहितेन खजे-नेव मथ्यमानस्य योऽणिमा स ऊर्ध्वः समुदीषति ; तन्मनोभवति, मनोवयवैः सह संभूय मन उपचिनोतीत्येतत् ॥
In plain words
Just as in this familiar example, O gentle one: when food is eaten and digested by the digestive fire in the belly—churned by the vital breath just as curds are churned with a churning stick—whatever subtle essence rises upward becomes the mind. Joining with other mental elements, it nourishes and builds up the mind.
Close to the Sanskrit
Just as this example: even so indeed, O gentle one, of food such as rice being eaten and enjoyed, churned by the gastric fire accompanied by wind like a churning stick, whichever subtle essence rises upward, that becomes the mind; uniting together with mental parts, it builds up the mind—this is it.