Applescript: Recursive Folders of Selected Folder - iteration

Question

Using applescript, I'm trying to create a .patch file in a set of parallel folders for every .recipe file in a target folder and its sub-folders. This also includes creating a parallel folder structure as the script does it's thing. I've got the steps right, but some part of the detailed grammar is wrong and I can't figure out what and how to fix it. Debugging information I've read so far has not helped me, though I'm sure this is a simple matter of incorrect applescript grammar. Here is the code:
use AppleScript version "2.4" -- Yosemite (10.10) or later
use scripting additions
on run
set patchFile to (choose file with prompt "Select patch file...")
set assetsFolder to (choose folder with prompt "Select recipe assets folder...")
set dumpFolder to (choose folder with prompt "Select dump folder...")
makePatches(patchFile, assetsFolder, dumpFolder)
end run
on makePatches(patchFile, targetFolder, dumpFolder)
tell application "Finder"
set recipeCount to count (files in folder (targetFolder) whose name ends with ".recipe")
if (recipeCount > 0) then
set recipeFiles to files in folder (targetFolder) whose name ends with ".recipe"
repeat with eachFile in recipeFiles
set recipePatch to duplicate patchFile to folder dumpFolder
set recipePatch's name to eachFile's name & ".patch"
end repeat
end if
set folderCount to (folders in folder (targetFolder) whose visible is true)
if (folderCount > 0) then
set subFolders to folders in folder (targetFolder)
repeat with eachFolder in subFolders
set newName to folder eachFolder's name
set newFolder to make new folder at folder dumpFolder
set newFolder's name to newName
my makePatches(patchFile, eachFolder, newFolder)
end repeat
end if
end tell
return
end makePatches
Note that if I remove the code for iterating through the folders and simply have it create patches for each .recipe file in a folder, then that code works. Or at least, it does as far as I can tell. So the problem should be somewhere at or after folderCount. The recursion is needed, as is the ability to use choose with prompt. Hopefully that isn't a problem. What is the correct grammar for the iteration section?

Answer 1

After semi-blindly adjusting the code and looking at just about every relevant example I could find, I came up with some code that does exactly what is needed. But I don't really understand what was going wrong with the original, so while I'll post the working code I made, I'd still like to hear what was wrong with the original code explained.
on run
set patchFile to (choose file with prompt "Select patch file...")
set assetsFolder to (choose folder with prompt "Select recipe assets folder...")
set dumpFolder to (choose folder with prompt "Select dump folder...")
makePatches(patchFile, assetsFolder, dumpFolder)
end run
on makePatches(patchFile, targetFolder, dumpFolder)
tell application "Finder"
set recipeFiles to files of targetFolder whose name ends with ".recipe"
repeat with eachFile in recipeFiles
set recipePatch to duplicate patchFile to dumpFolder
set recipePatch's name to eachFile's name & ".patch"
end repeat
end tell
tell application "Finder" to set theseSubFolders to folders of targetFolder
repeat with tSubF in theseSubFolders
set newName to tSubF's name
tell application "Finder" to set newFolder to (make new folder at dumpFolder with properties {name:newName})
my makePatches(patchFile, tSubF, newFolder)
end repeat
end makePatches