Here is a pattern for a knitted sandwich with visible cheese.
What you need
Fawn or Cream Wool
Cast on 25 stitches.
Garter Stitch until your work makes a square the size of bread. Cast Off.
With yellow cast on 22 stitches,
Decrease at each end until 1 stitch remains, fast off.
Place on bread and fold top over to make a triangle.
Fold square into a half on the triangle and Stitch cheese into middle.