In Western tradition, the Thursday after Trinity Sunday is the feast of Corpus Christi. It and Trinity Sunday are, as far as I recall, the only holidays that primarily celebrate a doctrine rather than a person or event. In its original (and present) Roman setting, Corpus Christi is a celebration of the doctrine of transubstantiation, which is the official Roman explanation for how the Body and Blood of Christ is present in the Sacrament of Holy Communion.
It is often incorrectly assumed that transubstantiation is the same as the doctrine of the corporeal real presence; that is incorrect. The former is an explanation of how the latter works; there are other theological theories that explain the doctrine of the real presence. If that confuses or surprises you, or you want to look at this in a little more detail, check out this summary.
Anyway, transubstantiation is explicitly ruled out in our formularies, so why would we ever want to celebrate Corpus Christi? Among the particularly high-church Anglo-Catholics, there have been a number of movements toward both reviving pre-Reformation tradition and aping the Church of Rome in the present. Corpus Christi was a major holiday in popular devotion as well as the calendar of the church, and in light of how lax many (perhaps most) Protestants treat Holy Communion, it seemed necessary to some to re-emphasize the holiness of Holy Communion with a restored feast day in its honor. Appropriated into Anglican tradition, one might call it “Thanksgiving for the gift of Holy Communion”, in a manner not unlike last week’s “Thanksgiving for the Promulgation of the First Prayer Book.”
Another angle of how and why Corpus Christi can be re-appropriated in Anglican tradition is the fact that the traditional Collect for this holiday was appointed by Thomas Cranmer to be the Collect for Maundy Thursday, and has remained unchanged ever since. Seriously, compare the Latin Mass propers in English with ours; it’s the same prayer! Combine this with the fact that one of the Scripture lessons is the same (Epistle is from 1 Corinthians 11), and you find that Corpus Christi is basically just a reiteration of Maundy Thursday outside the context of Holy Week, just as Holy Cross Day is a reiteration of Good Friday outside the context of Holy Week, and the (modern) Last Sunday of Epiphanytide is a reiteration of the feast of the Transfiguration in a different context.
If you want to commemorate an Anglican-style Corpus Christi, the easiest way to do it under the auspices of the 2019 Prayer Book is to do a Votive Mass of the Holy Eucharist according to the Various Occasion Propers on page 733, which instructs you to imitate Maundy Thursday. That would turn out as follows:
Almighty Father, whose most dear Son, on the night before he suffered, instituted the Sacrament of his Body and Blood: Mercifully grant that we may receive it in thankful remembrance of Jesus Christ our Savior, who in these holy mysteries gives us a pledge of eternal life; and who lives and reigns with you and the Holy Spirit, one God, for ever and ever. Amen.
Exodus 12:1-14; Psalm 78:15-26; 1 Corinthians 11:23-26(27-34); Luke 22:14-30
I took the liberty of removing the John 13 Gospel option as that is about the “maundy” and not about the Eucharist per se.
You might also consider other traditional Communion-related Psalms such as 34 or the latter part of 116. John 6:47-58 is also traditional Corpus Christi material, if you don’t mind applying that text to Eucharistic doctrine. Don’t forget, also, to grab a hymnal and sing or read some Communion hymns! Anglican hymnals have some truly wonderful entries in this category that you can’t find in most of the rest of the Protestant world, and a couple of my all-time favorite songs are Communion hymns. It’s definitely worth celebrating in song, too.