I have been working on developing an Orval clone for a couple of years and finally achieved what I wanted and I think what you are looking for. Here is what I did. For a 10 gallon batch: Using the grain bill of a dark saison and a yeast cultures from Orval and Moinette the beer reached 1.006 after the primary fermentation. After 3 weeks in a bright tank the beer was cold crashed at 32 degrees F (with gelatin) for a week. 3 days before bring the temp up to 56 degrees F a 1500 ml starter of Brett C (White Labs)was prepared. Transferring the beer to fresh, sterile, purged carboys, I pitched the Brett. After allowing the Brett work for 1 month at 56 degrees F, the gravity was down to just under 1.005 and I bottled using a fresh pitch of my Orval culture and bottle conditioned for 3 months at 56 degrees F. Six months after pitching the Brett, this was the best beer ever (my opinion). It is also my opinion that allowing the Brett to do it's work at cool temps creates the flavor profile you have described.