Combine all the ingredients except sheets in the filling and cook (on stove top or in slow cooker), until mince is done.
Using a oven proof dish layer sheets and filling, ending with sheets on top and cover with alfoil.
Place dish in the sc with a little water and cook on low for 5 hours.
Make the Bechmel by combining butter and flour in a small pot,adding flour in slowly over a low heat until it has a dough like quality and then slowly add milk whisking entire time.
Once it has been combined add in cheeses (reserving a little grated cheese for the top) and cook until cheeses have melted.
Pour on top of lasagna, put grated cheese that was reserved on top and grill till brown
NOTE - the filling freezes really well so I often double the mixture, and freeze for later to make either spaghetti bog, some more lasagna or top with mashed potato for cottage pie