Last night I made muffins, and along with adding shredded cheddar cheese to the muffins, I cut up a half-pound block of pepper jack into 1" by 1" by 1/2" chunks, and then poked one chunk into the top of each muffin. (Mostly, but not totally, sunk within the muffin.)
The muffin batter and cheese; I covered with another layer of batter.

The finished muffin cut open.

This created a well of gooey cheese in the center of each muffin, which is why they didn't last long enough to take pictures of. The pictures are from this morning's version.
However, it DID spill some cheese on the cookie sheet, but that was fairly easy to remove with a metal spatula. ETA: the completely covered cheese cubes don't spill so much.
Today's muffins were the basic recipe plus 1/2 cup sugar and a handful of raisins in the dry and 2 mashed bananas in the wet. Very tasty, but needed more sugar!

The muffin batter and cheese; I covered with another layer of batter.
The finished muffin cut open.
This created a well of gooey cheese in the center of each muffin, which is why they didn't last long enough to take pictures of. The pictures are from this morning's version.
However, it DID spill some cheese on the cookie sheet, but that was fairly easy to remove with a metal spatula. ETA: the completely covered cheese cubes don't spill so much.
Today's muffins were the basic recipe plus 1/2 cup sugar and a handful of raisins in the dry and 2 mashed bananas in the wet. Very tasty, but needed more sugar!